RapidStreamHasherV3 implementation, test, and benchmarks

[hoxxep]

This implements RapidStreamHasherV3 per #73, which is a stable Hasher-inspired interface for streaming but doesn't directly implement std::hash::Hasher due to hash portability/stability concerns. (Perhaps one day we'll finish PortableHash...)

I've also changed rapidhash_v3_file to use the RapidStreamHasherV3 to a nearly 2x throughput improvement, although the stream hasher is still around 2x faster in most cases due to the Read trait forcing us to copy into a local buffer.

A TODO(v5) is left to suggest a change to the rapidhash_v3_file_inline interface to support a BUFFER_SIZE parameter (or perhaps a runtime one).