Switch to alloy

[michaelsproul]

This is a staging PR for the switch from ethereum-types to alloy.

The plan is to get this PR integrated with Lighthouse and passing all tests prior to merging.

SigP contributors are free to push to this PR, or raise further PRs against it.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 10 lines in your changes missing coverage. Please review.

Project coverage is 80.54%. Comparing base (0b538a4) to head (06d9bcd).

Files	Patch %	Lines
ssz/src/decode/impls.rs	64.28%	5 Missing ⚠️
ssz/src/encode/impls.rs	68.75%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #21      +/-   ##
==========================================
+ Coverage   78.68%   80.54%   +1.86%     
==========================================
  Files          11       11              
  Lines         455      473      +18     
==========================================
+ Hits          358      381      +23     
+ Misses         97       92       -5     

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