Added clean_qgis_layer decorator back

[Joonalai]

This PR:

• Adds clean_qgis_layer decorator back since it has been requested

[Joonalai]

@LKajan, @ismogis could you review this?

[LKajan]

I think this kind of approach would indeed be cleaner than figuring by the function name the need for layer cleaning.

This particular implementation seems to fail in cases where the layer fixture is using yield:

@pytest.fixture()
@clean_qgis_layer
def layer():
  layer = QgsLayer(...)
  yield layer
  print(f"teardown layer {layer}")

Could you find some alternative way for the implementation?

Have you studied what actually is causing these seg faults? Is it possible to fix the root cause instead?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 66.66667% with 3 lines in your changes missing coverage. Please review.

Project coverage is 57.53%. Comparing base (d782092) to head (a466e4c).

Files	Patch %	Lines
src/pytest_qgis/utils.py	66.66%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #64      +/-   ##
==========================================
+ Coverage   57.25%   57.53%   +0.28%     
==========================================
  Files           7        7              
  Lines         496      504       +8     
==========================================
+ Hits          284      290       +6     
- Misses        212      214       +2     

Flag	Coverage Δ
pytest	57.53% <66.66%> (+0.28%)	⬆️

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[LKajan]

I added a mention that this doesn't work with fixtures that yield for now and made typing more precise.
With these changes I think it is ok to merge until we find a better solution to make sure map layers don't cause seg faults.