6. refactor(state): split database access into modules by Zebra types

[teor2345]

Motivation

As part of changing the database, we'll need to make sure all database accesses go through a well-defined API.

As the final step, we split reads and writes into modules by zebra_chain types.

This makes it easier to review changes, because the read and write formats are next to each other.

Solution

Code Movement:

• split reading and writing into block, transparent, shielded, chain, and metrics modules

Related Cleanups:

• split genesis note commitment trees from the genesis block check

Related Fixes:

• only change metrics after we've fully validated the block

Part of ticket #3151.

Based on PR #3607, feel free to move this PR out of draft after it merges.

Review

@oxarbitrage can review this PR.

git diff --color-moved could make the review a lot easier.

Reviewer Checklist

• Code moves are correct
• Existing tests pass

Follow Up Work

• add state snapshot tests - I'll get Janito to review my next PRs
• start changing the state format

[codecov]

Codecov Report

Merging #3617 (b990048) into main (4fc10e5) will increase coverage by 0.05%.
The diff coverage is 97.05%.

@@            Coverage Diff             @@
##             main    #3617      +/-   ##
==========================================
+ Coverage   79.94%   80.00%   +0.05%     
==========================================
  Files         281      285       +4     
  Lines       32722    32735      +13     
==========================================
+ Hits        26160    26190      +30     
+ Misses       6562     6545      -17     

[teor2345]

@oxarbitrage this PR is ready for review now - it's the last refactor PR.

Thanks for sticking with this!

[oxarbitrage]

nice one