WIP - tidying eligibility filters

[DJViau]

This is just almost entirely cleanup.

• It just shuffles around the functions so that all the helpers are at the top and the filters follow.
• It also cleans up one naming convention violation I perpetrated a while back.
• It adds some quick and dirty comments.

One logic change:

• It removes superfluous ineligibility criteria on one filter (we were treating match* functions as ineligible when it seems they were eligible). I fuzzed for an hour and a half or so and didn't hit any issues, but I'm not sure how frequently the mutation gets hit and whether an hour and a half of fuzzing is even enough for confidence in the relatively frequently hit mutations these days.

IMO this is mergable now if we want it in ASAP (to avoid merge conflicts) but I'm planning on coming back to it and working more on this branch once I get the docs updates done.

EDIT: This now also includes a bunch of comments on the whats and whys of some mutations. Still a WIP but imo still could be merged at any point.

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (4d7bfc5) 100.00% compared to head (c24a7d7) 100.00%.

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Additional details and impacted files

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##              main     #1206   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           46        46           
  Lines         2652      2652           
  Branches       396       396           
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  Hits          2652      2652           

Flag	Coverage Δ
foundry	77.80% <ø> (ø)
production	100.00% <ø> (ø)
reference	100.00% <ø> (ø)

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