Adding option to pytest to skip regression tests

[germa89]

Add argument to pytest CLI to skip image regresion check in all tests.

This is also a request from MAPDL building team.

Example

pytest -k "subset_tests" --skip-regression-check

[codecov]

Codecov Report

Merging #2350 (dfc1a72) into main (dc64d46) will decrease coverage by 0.02%.
Report is 3 commits behind head on main.
The diff coverage is 87.50%.

@@            Coverage Diff             @@
##             main    #2350      +/-   ##
==========================================
- Coverage   87.63%   87.61%   -0.02%     
==========================================
  Files          45       45              
  Lines        8513     8518       +5     
==========================================
+ Hits         7460     7463       +3     
- Misses       1053     1055       +2