feat: apply promisifyStream to ProcessPromise exposed streams

[antongolub]

We've previously added stream extensions to make support mixed piping:

await $`cmd`.pipe(transform).pipe`cmd`

Let's also apply the same approach for ProcessPromise exposed streams:

const p1 = $`cmd`

const p2 = p.stdout.pipe`cmd1`
const p3 = p.stderr.pipe`cmd2`

See util.ts#promisifyStream for details

[antongolub]

const p2 = p.pipe.stdout`cmd1`
const p3 = p.pipe.stderr`cmd2`

[antonmedv]

Why do we need those APIs?

[antongolub]

We can redirect error stream to the next piped process via 2>&1, but not stdall.