* Remove reference to removed dir 'third_party/rust_crates'.
* Remove reference to unused environment variable 'DENO_NINJA_PATH'.
* Remove helper functions 'root()' and 'tp()'.
* Move definition of 'third_party_path' to build.py.
* Move definition of 'gn_exe()' to setup.py.
* Move 'download_sccache()' and 'download_hyperfine()' from prebuilt.py
  to third_party.py, and delete prebuilt.py.
* Add helper function 'get_platform_dir_name()' to locate the
  platform-specific 'v8/buildtools/<platform>' and
  'prebuilt/<platform>' directories.
* Add helper function 'get_prebuilt_tool_path()' that returns the full
  path to a platform-specific executable in //prebuilt.
* Cosmetic improvements.

Co-authored-by: NBartek Iwańczuk <biwanczuk@gmail.com>

Don't mix every http request in with the tests output.
Don't print that the file servers are starting unless
-vv flag is passed.

Capture the output of run with run_output which returns
stdout, stderr and exit_code. Test against this rather
than relying on sys.exit.

* use subclass of unittest.TestCase for all test cases

* allow to run single test file (eg. python tools/integration_tests.py)

* test filtering (via --pattern/-p CLI flag)

* use common CLI parser for all tests:
  usage: test.py [-h] [--failfast] [--verbose] [--executable EXECUTABLE]
               [--release] [--pattern PATTERN] [--build-dir BUILD_DIR]

  optional arguments:
  -h, --help            show this help message and exit
  --failfast, -f        Stop on first failure
  --verbose, -v         Verbose output
  --executable EXECUTABLE
                        Use external executable of Deno
  --release             Test against release executable
  --pattern PATTERN, -p PATTERN
                        Run tests that match provided pattern
  --build-dir BUILD_DIR
                        Deno build directory

* respect NO_COLOR variable

Move every test to a method on DenoTestCase.
test.py is a single TestSuite of every TestCase.

Add a Spawn context manager for http_server,
this is explicitly used where it's needed.
Each python test file can now be run independently
without needing to manually run http_server.

Add --help and consistent flags using argparse for
each python test, including --failfast.

Use ColorTextTestRunner so that '... ok' is green.

Properly discovers the permissions needed for each test.

Previously run_node.py would always attempt to remove and then re-create
the 'target/xx/node_modules' symlink. This causes sporadic build errors
on windows when multiple build targets that use run_node.py are being
built concurrently.

This is more optimial and this fixes a problem where occasionally
remove_and_symlink will error with:

    gen/compiler_bundle/main.js --sourcemapFile /Users/rld/src/deno --silent
    Traceback (most recent call last):
      File "../../tools/run_node.py", line 18, in <module>
        util.remove_and_symlink(target_rel, "node_modules", True)
      File "/Users/rld/src/deno/tools/util.py", line 103, in remove_and_symlink
        symlink(target, name, target_is_dir)
      File "/Users/rld/src/deno/tools/util.py", line 141, in symlink
        os.symlink(target, name)
    OSError: [Errno 17] File exists

It's annoying, and it also makes appveyor slow because it will re-upload
the third_party cache every time something changes in there.

Checks the output more carefully. The first line of output from
js/unit_tests.ts should be something like "running 96 tests"
And the last line should be something like
"test result: ok. 96 passed; 0 failed; 0 ignored; 0 measured; 36
filtered out"
This parses those strings and make sure they align.

This will catch silent death bugs.

Fixes #865.

Moves 'gn gen' into setup.py

Make tools/build.py more ergonomic.

* Make sync_third_party work in general
* Un-break build.py and run_hooks.py on windows
* Partially fix format.py on windows
* Reduce code duplication between run_hooks and sync_third_party

And use third_party/depot_tools/gn.