ci: use setup-fortran, use major version tags for actions

[wpbonelli]

• use fortran-lang/setup-fortran instead of modflowpy/install-gfortran-action (latter to be retired soon)
• use major version instead of full version tags for actions (less upkeep, fewer dependabot PRs)
• consolidate gcc test jobs in single matrix
• test gcc 11-13
• test python 3.11

[codecov]

Codecov Report

Merging #139 (3a1a31c) into master (a67f11b) will decrease coverage by 0.291%.
The diff coverage is n/a.

@@              Coverage Diff              @@
##            master      #139       +/-   ##
=============================================
- Coverage   81.630%   81.340%   -0.291%     
=============================================
  Files           20        20               
  Lines         3446      3446               
=============================================
- Hits          2813      2803       -10     
- Misses         633       643       +10     

see 2 files with indirect coverage changes

[wpbonelli]

@jdhughes-usgs I considered consolidating gcc in a single matrix with 11-13 since 10 and below are out of maintenance but didn't know if there were good reasons to keep the max at 11 (e.g., maybe some programs can't be built with newer gcc). Do you have any objections?

[wpbonelli]

Updated to gcc 11-13 and python 3.8-3.11, all seems to build ok. There is a pytest issue to resolve with python 3.12, I will take a second look at it sometime but for now this should be ok to go