This commit adds `SubprocessReadableStream` interface that are used
for `ChildProcess.stdout` and `ChildProcess.stderr`. It's an extension
to a regular `ReadableStream` that provides convenience methods to collect
the output and parse it with `.bytes()`, `.arrayBuffer()`, `.text()` and
`.json()` helper methods (similarly to the ones available on `Response`).
Closes https://github.com/denoland/deno/issues/30323
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Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>