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 :warning:

Additional details and impacted files

```diff @@ 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](https://app.codecov.io/gh/GispoCoding/pytest-qgis/pull/64/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GispoCoding) | Coverage Δ | | |---|---|---| | [pytest](https://app.codecov.io/gh/GispoCoding/pytest-qgis/pull/64/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GispoCoding) | `57.53% <66.66%> (+0.28%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GispoCoding#carryforward-flags-in-the-pull-request-comment) to find out more.

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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.