♻️⚡ optimize implementation of collectBlocks

[burgholzer]

Description

This PR slightly optimizes the implementation of the collectBlocks optimization pass introduced in #581.

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 91.3%. Comparing base (63fdf10) to head (df85778).

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #584   +/-   ##
=====================================
  Coverage   91.3%   91.3%           
=====================================
  Files        132     132           
  Lines      14043   14052    +9     
  Branches    2244    2243    -1     
=====================================
+ Hits       12832   12841    +9     
  Misses      1211    1211           

Flag	Coverage Δ
cpp	91.0% <100.0%> (+<0.1%)	⬆️
python	99.5% <ø> (ø)

Files	Coverage Δ
include/mqt-core/operations/CompoundOperation.hpp	100.0% <ø> (ø)
src/CircuitOptimizer.cpp	88.3% <100.0%> (-0.1%)	⬇️
src/operations/CompoundOperation.cpp	83.3% <100.0%> (+2.6%)	⬆️