Move signature validator module into shared

[vkgnosis]

This module is needed in orderbook and autopilot. Later I might do a fine grained refactor move some things out of shared again.

No logic change.

Test Plan

CI

[nlordell]

fine grained refactor move some things out of shared again.

Is there value to having a crate specifically for shared components between orderbook and api?

[vkgnosis]

There might be. It's going to be easier to track down the dependencies when the autopilot stuff is done. I'm going to re-visit it then.

[codecov-commenter]

Codecov Report

Merging #406 (e4e8217) into main (e2da212) will decrease coverage by 0.00%.
The diff coverage is 10.52%.

❗ Current head e4e8217 differs from pull request most recent head 79e11bc. Consider uploading reports for the commit 79e11bc to get more accurate results

@@            Coverage Diff             @@
##             main     #406      +/-   ##
==========================================
- Coverage   64.08%   64.07%   -0.01%     
==========================================
  Files         221      222       +1     
  Lines       41851    41848       -3     
==========================================
- Hits        26819    26816       -3     
  Misses      15032    15032