[C++] Document the guarantees of ChunkResolver::Resolve and minimize branching

[felipecrv]

Describe the enhancement requested

The invariants of ChunkResolver and pre-conditions of ChunkResolver::Resolve() are unclear which can lead to multiple problems:

1. Misuse
2. Misunderstanding that leads to addition of more checks that can kill speculative execution in tight loops
3. Missed micro-optmization opportunities

Request: document the class and implement possible micro-optmizations.

Component(s)

C++