tests: Improves testing for all the fork logic so that the tests never fail

[0xJepsen]

What I did:

• Used rayon to run a bunch of iterations of the tests concurrently
• Cleaned up files after every iteration so that every PR no longer has a dif if tests were run.
• Used assertions on results to check is_ok()

I also got roasted by chat gpt when i was asking it if i could grab any functionality from the binary into the lib. said that if this is the case it's an indication i should move the logic from the bin to the lib. I think this is correct long term but for now i just moved the fork_into_arbiter test into the bin tests since it was able to get everything we needed. Did some small cleanup around this to make it easier more modular for the future.

This PR also changes CI to run on every PR now, not just ones into main.

[codecov]

Codecov Report

Merging #597 (63b01de) into arbiter/version (1ee29f9) will decrease coverage by 2.87%.
The diff coverage is 87.30%.

❗ Current head 63b01de differs from pull request most recent head 167861b. Consider uploading reports for the commit 167861b to get more accurate results

@@                 Coverage Diff                 @@
##           arbiter/version     #597      +/-   ##
===================================================
- Coverage            63.56%   60.69%   -2.87%     
===================================================
  Files                   25       26       +1     
  Lines                 4394     5427    +1033     
===================================================
+ Hits                  2793     3294     +501     
- Misses                1601     2133     +532     

Files	Coverage Δ
arbiter-core/src/bindings/weth.rs	46.49% <ø> (ø)
bin/fork/tests.rs	95.52% <94.44%> (-4.48%)	⬇️
bin/fork/mod.rs	88.34% <44.44%> (-2.66%)	⬇️

... and 2 files with indirect coverage changes

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