Implement TreeHash for bitfield

[macladson]

In preparation for EIP-7495, bitfield has been moved to https://github.com/sigp/ethereum_ssz.

This PR implements TreeHash for both BitVector and BitList for those types.

Requires sigp/ethereum_ssz#25

[codecov]

Codecov Report

Attention: Patch coverage is 68.75000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 79.67%. Comparing base (12d828c) to head (2536b81).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
tree_hash/src/impls.rs	68.75%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #18      +/-   ##
==========================================
+ Coverage   79.66%   79.67%   +0.01%     
==========================================
  Files           6        6              
  Lines         295      310      +15     
==========================================
+ Hits          235      247      +12     
- Misses         60       63       +3     

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[michaelsproul]

New release is out for ethereum_ssz:

https://github.com/sigp/ethereum_ssz/releases/tag/v0.8.0

[paulhauner]

I could use this one for sigp/lighthouse#6609, any chance we can get it merged? 🙏

My understanding is that @macladson needs to add a tree-hash test to satisfy teh bot.

[michaelsproul]

The bot isn't meant to block the merge due to this config:

tree_hash/.github/workflows/test-suite.yml

Line 52 in 12d828c

informational: true

We can just ignore it for now

[michaelsproul]

I'll add a test anyway, seeing as 0% coverage looks terrible.