feat(util-stream): splitStream and headStream utilities

[kuhe]

• splitStream splits a stream into two streams using pipe(PassThrough) or tee() depending on Stream type.
• headStream collects the first N bytes of a stream.

Use case: peek the head of a stream's copy while leaving the 2nd copy of that original stream intact

Use case: obtain a parallel stream for checksumming

[kuhe]

I've tested this for memory leaks. As long as the additional split stream reaches reference count 0 it will be garbage collected without needing to explicitly call its destructor or draining it.