Use tempfile instead of protected TempPathFactory in QGIS config path creation

[Joonalai]

When using pytest-qgis with pytest-xdist plugin on Windows, the following errors occur:

PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: '\\\\?\\C:\\Users\\foo\\AppData\\Local\\Temp\\pytest-of-foo\\pytest-177\\popen-gw0\\qgis-test0\
\profiles\\default\\qgis-auth.db'

This is caused by creating temporary path for QGIS using pytest's internal TempPathFactory, which is not ment to be used by the plugins or in hooks...

This PR suggests a change to use tempfile module instead of TempPathFactory in QGIS config path creation. This is to allow using pytest-xdist plugin to run tests in parallel. In addition plugin pytest-rerunfailures can be used to rerun tests failing randomly with segmentation faults.

This PR also adds a mention about importing modules in conftest to resolve #35.

[codecov-commenter]

Codecov Report

Patch coverage: 66.66% and project coverage change: -0.02 ⚠️

Comparison is base (bc9adc6) 54.68% compared to head (86dec5c) 54.66%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #34      +/-   ##
==========================================
- Coverage   54.68%   54.66%   -0.02%     
==========================================
  Files           7        7              
  Lines         470      472       +2     
==========================================
+ Hits          257      258       +1     
- Misses        213      214       +1     

Flag	Coverage Δ
pytest	54.66% <66.66%> (-0.02%)	⬇️

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Impacted Files	Coverage Δ
src/pytest_qgis/pytest_qgis.py	52.67% <66.66%> (-0.03%)	⬇️

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[lehtojaa]

Looks good!