🚨 fix Qiskit 1.2 deprecation warnings

[burgholzer]

Description

Fixes all the deprecation warnings raised by Qiskit 1.2.
A warning filter still has to be applied since Qiskit itself imports deprecated code on the default path. This should be fixed in a follow-up release.

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 87.0%. Comparing base (89f18fb) to head (91d77f5).
Report is 99 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #673   +/-   ##
=====================================
  Coverage   87.0%   87.0%           
=====================================
  Files        125     125           
  Lines      13781   13781           
  Branches    2164    2164           
=====================================
  Hits       11996   11996           
  Misses      1785    1785           

Flag	Coverage Δ		*Carryforward flag
cpp	86.6% <ø> (ø)		Carriedforward from d98f8cd
python	99.7% <100.0%> (ø)

*This pull request uses carry forward flags. Click here to find out more.

Files with missing lines	Coverage Δ
src/mqt/core/plugins/qiskit.py	100.0% <100.0%> (ø)