* Refactoring: part 1

* Refactoring: part 2

* Handle request using ReadBuffer interface

* Struggles with ReadBuffer's

* Fix URI parsing

* Implement parsing of multipart/form-data

* Check HTTP_LENGTH_REQUIRED before eof() or will hang

* Fix HTTPChunkedReadBuffer

* Fix build and style

* Fix test

* Resist double-eof

* Fix arcadian build

In [1] stress tests found:

    2021.02.12 14:20:58.800988 [ 17728 ] {de3e7894-b401-4f7d-8530-90cd5ab06682} <Debug> executeQuery: (from [::1]:45792, using production parser) (comment: /usr/share/clickhouse-test/queries/0_stateless/01520_client_print_query_id.expect) SELECT * FROM numbers(34599)
    2021.02.12 14:20:58.916484 [ 17728 ] {de3e7894-b401-4f7d-8530-90cd5ab06682} <Trace> ContextAccess (default): Access granted: CREATE TEMPORARY TABLE ON *.*
    2021.02.12 14:20:59.071980 [ 17728 ] {de3e7894-b401-4f7d-8530-90cd5ab06682} <Trace> InterpreterSelectQuery: FetchColumns -> Complete
    2021.02.12 14:21:10.708202 [ 17728 ] {de3e7894-b401-4f7d-8530-90cd5ab06682} <Information> executeQuery: Read 34599 rows, 270.30 KiB in 11.876294055 sec., 2913 rows/sec., 22.76 KiB/sec.
    2021.02.12 14:22:10.506261 [ 17728 ] {de3e7894-b401-4f7d-8530-90cd5ab06682} <Debug> DynamicQueryHandler: Done processing query
    2021.02.12 14:22:18.238037 [ 375 ] {} <Fatal> BaseDaemon: (version 21.3.1.5996, build id: 8DBCED54529C989F7AD4D991F51410774D55DE6C) (from thread 17728) Terminate called for uncaught exception:
    Code: 24, e.displayText() = DB::Exception: Cannot write to ostream at offset 262994, Stack trace (when copying this message, always include the lines below):

    0. ./obj-x86_64-linux-gnu/../contrib/libcxx/include/exception:0: Poco::Exception::Exception(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, int) @ 0x15c976cb in /usr/bin/clickhouse
    1. ./obj-x86_64-linux-gnu/../src/Common/Exception.cpp:56: DB::Exception::Exception(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, int, bool) @ 0x8c9320e in /usr/bin/clickhouse
    2. ./obj-x86_64-linux-gnu/../src/IO/WriteBufferFromOStream.cpp:0: DB::WriteBufferFromOStream::nextImpl() @ 0x8d54da5 in /usr/bin/clickhouse
    3. ./obj-x86_64-linux-gnu/../src/IO/BufferBase.h:39: DB::WriteBufferFromOStream::~WriteBufferFromOStream() @ 0x8d551d7 in /usr/bin/clickhouse
    4. ./obj-x86_64-linux-gnu/../src/IO/WriteBufferFromOStream.cpp:44: DB::Write

    2021.02.12 14:22:18.811071 [ 18134 ] {} <Fatal> BaseDaemon: ########################################
    2021.02.12 14:22:18.878935 [ 18134 ] {} <Fatal> BaseDaemon: (version 21.3.1.5996, build id: 8DBCED54529C989F7AD4D991F51410774D55DE6C) (from thread 17728) (query_id: de3e7894-b401-4f7d-8530-90cd5ab06682) Received signal Aborted (6)
    2021.02.12 14:22:18.943148 [ 18134 ] {} <Fatal> BaseDaemon:
    2021.02.12 14:22:19.007073 [ 18134 ] {} <Fatal> BaseDaemon: Stack trace: 0x7f109932018b 0x7f10992ff859 0x8bb33ae 0x8e301dd 0x17dac8c4 0x17dac7c7 0x8c3fe0b 0x8d552c5 0x8d552ea 0x11a29914 0x11a2a2ca 0x12f96092 0x12f8c65e 0x12f84300 0x15b84110 0x15bc0913 0x15bc103f 0x15d29a12 0x15d27fb0 0x15d267b8 0x8badbad 0x7f10994d5609 0x7f10993fc293
    2021.02.12 14:22:19.255998 [ 18134 ] {} <Fatal> BaseDaemon: 5. raise @ 0x4618b in /usr/lib/x86_64-linux-gnu/libc-2.31.so
    2021.02.12 14:22:19.270203 [ 18134 ] {} <Fatal> BaseDaemon: 6. abort @ 0x25859 in /usr/lib/x86_64-linux-gnu/libc-2.31.so
    2021.02.12 14:22:50.108918 [ 370 ] {} <Fatal> Application: Child process was terminated by signal 6.

  [1]: https://clickhouse-test-reports.s3.yandex.net/19580/6aecb62416ece880cbb8ee3a803e14d841388dde/stress_test_(thread).html#fail1

Verified locally by commenting out->next() call in
WriteBufferFromHTTPServerResponse::nextImpl(), adding a sleep(1) and
canceling HTTP request before it finished, the stacktrace as follow:

    [ 6351 ] {} <Fatal> BaseDaemon: (version 21.3.1.1, build id: 9B40466BF3D2F5AED78A52A995A4A2FD3116787C) (from thread 6677) Terminate called for uncaught exception:
    Code: 24, e.displayText() = DB::Exception: Cannot write to ostream at offset 4, Stack trace (when copying this message, always include the lines below):

    0. /src/ch/clickhouse/.cmake/../src/Common/StackTrace.cpp:298: StackTrace::tryCapture() @ 0x30a52a in /src/ch/clickhouse/.cmake/src/libclickhouse_common_iod.so
    1. /src/ch/clickhouse/.cmake/../src/Common/StackTrace.cpp:260: StackTrace::StackTrace() @ 0x30a4e5 in /src/ch/clickhouse/.cmake/src/libclickhouse_common_iod.so
    2. /src/ch/clickhouse/.cmake/../src/Common/Exception.cpp:53: DB::Exception::Exception(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int, bool) @ 0x2a61ae in /src/ch/clickhouse/.cmake/src/libclickhouse_common_iod.so
    3. /src/ch/clickhouse/.cmake/../src/IO/WriteBufferFromOStream.cpp:22: DB::WriteBufferFromOStream::nextImpl() @ 0x3b468a in /src/ch/clickhouse/.cmake/src/libclickhouse_common_iod.so
    4. /src/ch/clickhouse/.cmake/../src/IO/WriteBuffer.h:47

    <snip>
    [ 8966 ] {} <Fatal> BaseDaemon: 7. __cxxabiv1::__terminate(void (*)()) @ 0x1784ca in /src/ch/clickhouse/.cmake/contrib/replxx-cmake/libreplxxd.so
    <snip>
    [ 8966 ] {} <Fatal> BaseDaemon: 10. /src/ch/clickhouse/.cmake/../src/IO/WriteBufferFromOStream.cpp:0: DB::WriteBufferFromOStream::~WriteBufferFromOStream() @ 0x3b48c1 in /src/ch/clickhouse/.cmake/src/libclickhouse_common_iod.so
    [ 8966 ] {} <Fatal> BaseDaemon: 11. /src/ch/clickhouse/.cmake/../src/IO/WriteBufferFromOStream.cpp:44: DB::WriteBufferFromOStream::~WriteBufferFromOStream() @ 0x3b48ec in /src/ch/clickhouse/.cmake/src/libclickhouse_common_iod.so
    <snip>
    [ 8966 ] {} <Fatal> BaseDaemon: 14. /src/ch/clickhouse/.cmake/../src/IO/WriteBufferFromHTTPServerResponse.cpp:218: DB::WriteBufferFromHTTPServerResponse::~WriteBufferFromHTTPServerResponse() @ 0x3b33cd in /src/ch/clickhouse/.cmake/src/libclickhouse_common_iod.so
    <snip>
    [ 8966 ] {} <Fatal> BaseDaemon: 22. /src/ch/clickhouse/.cmake/../src/Server/HTTPHandler.h:43: DB::HTTPHandler::Output::~Output() @ 0x260421 in /src/ch/clickhouse/.cmake/src/libclickhouse_serverd.so
    [ 8966 ] {} <Fatal> BaseDaemon: 23. /src/ch/clickhouse/.cmake/../src/Server/HTTPHandler.cpp:778: DB::HTTPHandler::handleRequest(Poco::Net::HTTPServerRequest&, Poco::Net::HTTPServerResponse&) @ 0x253fd4 in /src/ch/clickhouse/.cmake/src/libclickhouse_serverd.so

Since this hides real problems, since destructor does final flush and if
it fails, then data will be lost.

One of such examples if MEMORY_LIMIT_EXCEEDED exception, so lock
exceptions from destructors, by using
MemoryTracker::LockExceptionInThread to block these exception, and allow
others (so std::terminate will be called, since this is c++11 with
noexcept for destructors by default).

Here is an example, that leads to empty block in the distributed batch:

    2021.01.21 12:43:18.619739 [ 46468 ] {7bd60d75-ebcb-45d2-874d-260df9a4ddac} <Error> virtual DB::CompressedWriteBuffer::~CompressedWriteBuffer(): Code: 241, e.displayText() = DB::Exception: Memory limit (for user) exceeded: would use 332.07 GiB (attempt to allocate chunk of 4355342 bytes), maximum: 256.00 GiB, Stack trace (when copying this message, always include the lines below):

    0. DB::Exception::Exception<>() @ 0x86f7b88 in /usr/bin/clickhouse
    ...
    4. void DB::PODArrayBase<>::resize<>(unsigned long) @ 0xe9e878d in /usr/bin/clickhouse
    5. DB::CompressedWriteBuffer::nextImpl() @ 0xe9f0296 in /usr/bin/clickhouse
    6. DB::CompressedWriteBuffer::~CompressedWriteBuffer() @ 0xe9f0415 in /usr/bin/clickhouse
    7. DB::DistributedBlockOutputStream::writeToShard() @ 0xf6bed4a in /usr/bin/clickhouse

* Move some code outside dbms/src folder
* Fix paths

HTTP Accept-Encoding: br; Revert using unbundled brotli library. FCixed using not initialized http respones ostream pointer

HTTP Accept-Encoding: br; Expended ZlibCompressionMethod to generic CompressionMethod; Added brotli to CompressionMethod enum

    Core/Progress.h -> IO/Progress.h
    tests: sudo --non-interactive
    Fix freebsd link

The built-in clang doesn’t support value() for
`std::experimental::optional`. It however supports
dereference operator, which is basically the
same thing:

```
/clickhouse/dbms/src/DataStreams/NullableAdapterBlockInputStream.cpp:83:67: error: call to unavailable member function 'value':
                    res.insert({elem.column, elem.type, rename[i].value()});
                                                        ~~~~~~~~~~^~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/experimental/optional:547:17: note: candidate function has been explicitly made unavailable
    value_type& value()
                ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/experimental/optional:539:33: note: candidate function has been explicitly made unavailable
    constexpr value_type const& value() const
```