♻️🩹 fix and improve MQT Core linking

[burgholzer]

Description

A follow-up to #444 that fixes a particular linking issue and furthermore improves the overall library link time dependencies by removing the template code from the StateGenerator and moving the code to the .cpp file.

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

Attention: Patch coverage is 94.11765% with 4 lines in your changes missing coverage. Please review.

Project coverage is 95.3%. Comparing base (c634603) to head (dc4841b).
Report is 80 commits behind head on main.

Files with missing lines	Patch %	Lines
src/checker/dd/simulation/StateGenerator.cpp	94.1%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #446     +/-   ##
=======================================
- Coverage   95.4%   95.3%   -0.2%     
=======================================
  Files         40      40             
  Lines       1839    1838      -1     
  Branches     224     224             
=======================================
- Hits        1755    1752      -3     
- Misses        84      86      +2     

Flag	Coverage Δ
cpp	95.6% <94.1%> (-0.2%)	⬇️
python	94.0% <ø> (ø)

Files with missing lines	Coverage Δ
include/checker/dd/simulation/StateGenerator.hpp	100.0% <ø> (+4.1%)	⬆️
src/checker/dd/simulation/StateGenerator.cpp	94.8% <94.1%> (-5.2%)	⬇️

... and 1 file with indirect coverage changes