This adds a new op to get a single env var.

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

Previously: dial("tcp", "deno.land:80")
Now: dial({ hostname: "deno.land", port: 80, transport: "tcp" })
Similarly with listen().

When the global timer fires earlier than expected, which apparently
happens sometimes on server editions of Windows, we didn't call any
setTimeout callbacks, but we *also* didn't reschedule the global timer
to fire again later.

When this situation occurred it would make deno exit abruptly if there
were no other asynchronous ops running on the event loop. It could also
lead to application hangs if the upcoming setTimeout callback was
critical for the application to make progress.

Fixes #2933

The yarn.lock file is moved from //third_party to the root of
the main repository. This is where other package metadata
files (e.g. Cargo.lock and package.json) are also located.

This removes the EventListener, EventInit and CustomEventInit constructors from the userland globals. The type exports stay.

I removed the internal classes as well. EventListener's implementation seemed to be doing some bookkeeping on handled events but that's not being used anywhere so I assume it's old debug stuff. The other two are completely redundant.

This ensures the deno executable is properly created before running the integration tests.

Also allows deno_cli to be used as a lib. Docs are now properly generated: https://docs.rs/deno_cli/0.18.4/deno_cli/

Towards #2933
Prep for #2955

and remove DENO_NINJA_PATH from manual

Change submodule names to match the name of the corresponding github
repository, which is easier to remember than using the full path where
the submodule is (or used to be) checked out.