Fixes #3726

This PR provides support for referencing other lib files (like lib.dom.d.ts that are not
used by default in Deno.

* remove run_worker_loop, impl poll for WebWorker
* store JoinHandle to worker thread

* rename methods on Worker related to module loading
* reorganize cli/lib.rs
* remove cli/progress.rs and cli/shell.rs

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

Example:

		$ python2 -c 'open("\x80\x7F", "w")'

		$ deno eval 'Deno.readDirSync(".")'
		thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', cli/ops/fs.rs:373:16
		note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
		fatal runtime error: failed to initiate panic, error 5
		Aborted (core dumped)

Before this commit they made deno panic, now they are silently skipped.
Not ideal but arguably better than panicking.

No test because what characters are and aren't allowed in filenames is
highly file system-dependent.

Closes #3950

Moves to using a minimal System loader for bundles generated by Deno.
TypeScript in 3.8 will be able to output TLA for modules, and the loader
is written to take advantage of that as soon as we update Deno to TS
3.8.

System also allows us to support `import.meta` and provide more ESM
aligned assignment of exports, as well as there is better handling of
circular imports.

The loader is also very terse versus to try to save overhead.

Also, fixed an issue where abstract classes were not being re-exported.

Fixes #2553
Fixes #3559
Fixes #3751
Fixes #3825
Refs #3301

* replace "AtomicUsize" with "u64" for field type on "Metrics"
* move "compiler_starts" field from "Metrics" to "GlobalState"

* rewrite test runner in Rust
* migrate "test" and "runTests" functions from std to "Deno" namespace
* use "Deno.test()" to run internal JS unit tests
* remove std downloads for Deno subcommands

* Use PathBuf for DenoSubcommand::Bundle's out_file
* Use PathBuf for DenoSubcommand::Format's files
* Use PathBuf for DenoSubcommand::Install's dir
* Use PathBuf for read/write whitelists

* establish basic event loop for workers
* make "self.close()" inside worker
* remove "runWorkerMessageLoop() - instead manually call global function 
  in Rust when message arrives. This is done in preparation for structured clone
* refactor "WorkerChannel" and use distinct structs for internal 
  and external channels;  "WorkerChannelsInternal" and "WorkerHandle"
* move "State.worker_channels_internal" to "Worker.internal_channels"
* add "WorkerEvent" enum for child->host communication; 
  currently "Message(Buf)" and  "Error(ErrBox)" variants are supported
* add tests for nested workers
* add tests for worker throwing error on startup

Fixes: #3925

deno builds successfully with VS2019, so no need to require VS2017.

* rename ThreadSafeState to State
* State stores InnerState wrapped in Rc and RefCell