Rename RootHash to Commitment based on ZIP-244

[teor2345]

Motivation

The goal of this PR is to make progress on the outstanding cleanups on the block commitment field from #881.

In ZIP-244, the root hash field is renamed to block commitment. This name is more generic, and will probably stay the same going forward.

Solution

Interactive replace using:

fastmod RootHash Commitment
fastmod root_hash commitment
fastmod root_bytes commitment_bytes
git mv zebra-chain/src/block/root_hash.rs zebra-chain/src/block/commitment.rs

All replacements were accepted.

Review

@dconnolly or @oxarbitrage just a quick search and replace PR that's blocking other issues.

Related Issues

Implements part of #1874 and #881, but doesn't finish either of them.

Follow Up Work

Finish #881
Do design for #1874

[dconnolly]

A thought: in (sapling|orchard)::commitments, because there are several (Note, Value), they are explicitly named as such, even if it's a little redundant based on module paths and context, etc. Would naming this BlockCommitment work? Or is that possibly a less accurate name than just Commitment. Hm.

[teor2345]

A thought: in (sapling|orchard)::commitments, because there are several (Note, Value), they are explicitly named as such, even if it's a little redundant based on module paths and context, etc. Would naming this BlockCommitment work? Or is that possibly a less accurate name than just Commitment. Hm.

I had expected we would use Commitment like Height and Hash:

use path::to::block;

const commitment: block::Commitment = Default::default();

[dconnolly]

I had expected we would use Commitment like Height and Hash:

use path::to::block;

const commitment: block::Commitment = Default::default();

OK yeah, sounds good. ✅