New range coder implementation.

Adds the following features:
- Precision can be controlled per CDF rather than per table.
- Overflow coding (using Elias gamma code) can be controlled per CDF.
- Adds separate ops for batched and indexed CDF references, both of which
  support switching precision and overflow.
- Can encode several tensors into the same bit stream by calling ops multiple
  times, referencing the same handle.
- Can encode multiple streams with a single op invocation by batching.

PiperOrigin-RevId: 421631670
Change-Id: I8b739e655635c294acb563d6d06d442e37347691

Author: Johannes Ballé