🩹fix loading circuits from PathLike objects

[burgholzer]

Description

This PR fixes a small oversight in the mqt.core.load method, where the method would not work if being passed a PathLike object that is not a string (e.g., a Path).
The changes in the PR make sure that such an object is appropriately converted to a string before being passed to the constructor.

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 (28dc65e) to head (4165c22).
Report is 3 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #681   +/-   ##
=====================================
  Coverage   87.0%   87.0%           
=====================================
  Files        125     125           
  Lines      13781   13781           
  Branches    2164    2164           
=====================================
  Hits       11995   11995           
  Misses      1786    1786           

Flag	Coverage Δ		*Carryforward flag
cpp	86.6% <ø> (ø)		Carriedforward from 28dc65e
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/__init__.py	100.0% <100.0%> (ø)