🐛 use fuzzy comparison for floating point in const evaluation equality check

[burgholzer]

Description

This PR fixes another small bug observed as part of #803, which only surfaced under macOS when using GCC as the compiler.
Turns out that GitHub's CodeQL was right after all and exact equality checks on floating point values can come back to bite you.
In this case, two computations of std::tan(1.0) resulted in values that were off by a single ULP.
Although I am not 100% certain how this can even happen, this PR works around any such errors by using a fuzzy floating point comparison with an epsilon on the order of 10-12.

Checklist:

• The pull request only contains commits that are related to it.
• I have added appropriate tests and documentation.
• I have made sure that all CI jobs on GitHub pass.
• The pull request introduces no new warnings and follows the project's style guidelines.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.2%. Comparing base (ba3aa86) to head (32f0a47).
Report is 8 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #809   +/-   ##
=====================================
  Coverage   92.2%   92.2%           
=====================================
  Files        126     126           
  Lines      13827   13827           
  Branches    2153    2153           
=====================================
+ Hits       12756   12758    +2     
+ Misses      1071    1069    -2     

Flag	Coverage Δ
cpp	92.0% <100.0%> (+<0.1%)	⬆️
python	99.7% <ø> (ø)

Files with missing lines	Coverage Δ
...e/ir/parsers/qasm3_parser/passes/ConstEvalPass.hpp	81.3% <100.0%> (+0.4%)	⬆️

... and 1 file with indirect coverage changes