Add custom macros and traits for testing floating point numbers for approximate equality

[helgee]

There was a yak that needed shaving...

[codecov]

Codecov Report

❌ Patch coverage is 95.66038% with 23 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.71%. Comparing base (5fd874a) to head (4cb50c1).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/lox-test-utils/src/approx_eq/results.rs	77.31%	22 Missing ⚠️
crates/lox-bodies/src/lib.rs	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #258      +/-   ##
==========================================
- Coverage   69.34%   68.71%   -0.64%     
==========================================
  Files          89       90       +1     
  Lines       21247    21461     +214     
==========================================
+ Hits        14734    14747      +13     
- Misses       6513     6714     +201     

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[codspeed-hq]

CodSpeed Performance Report

Merging #258 will not alter performance

_{Comparing he/approx-eq (4cb50c1) with main (5fd874a)}

Summary

✅ 3 untouched
⏩ 1 skipped¹

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩