Since "Deno.spawn()", "Deno.spawnSync()" and "Deno.spawnChild"
are getting deprecated, this commits rewrites all tests and utilities to
use "Deno.Command" API instead.
- "SpawnOutput" extends "ChildStatus" instead of composing it
- "SpawnOutput::stdout", "SpawnOutput::stderr", "Child::stdin",
"Child::stdout" and "Child::stderr" are no longer optional, instead
made them getters that throw at runtime if that stream wasn't set
to "piped".
- Remove the complicated "<T extends SpawnOptions = SpawnOptions>"
which we currently need to give proper type hints for the availability of
these fields. Their typings for these would get increasingly complex
if it became dependent on more options (e.g. "SpawnOptions::pty"
which if set should make the stdio streams unavailable)
This PR refactors the usages of delay utility in js unit testing. The same
utiliy is defined in several places with different names. This PR replaces those
usages with the one provided in std/async/delay.ts to improve the readability
and consistency of test code.
