refactor(recarray_utils): deprecate functions for numpy builtins

[wpbonelli]

• deprecate ra_slice(), suggest numpy.lib.recfunctions.repack_fields()
• deprecate recarray(), suggest numpy.core.records.fromrecords()
• add tests demonstrating equivalent usage
• replace occurrences in tests and notebooks
• update docstring examples
  • show output instead of assigning to variable
  • use doctest to verify examples run correctly

Maybe worth doctesting in CI in future?

[codecov]

Codecov Report

Merging #1960 (409f60c) into develop (5b5eb4e) will increase coverage by 0.0%.
Report is 2 commits behind head on develop.
The diff coverage is 83.3%.

@@           Coverage Diff           @@
##           develop   #1960   +/-   ##
=======================================
  Coverage     72.6%   72.7%           
=======================================
  Files          257     257           
  Lines        57801   57800    -1     
=======================================
+ Hits         42018   42023    +5     
+ Misses       15783   15777    -6     

Files	Coverage Δ
flopy/utils/__init__.py	100.0% <100.0%> (ø)
flopy/utils/modpathfile.py	85.9% <100.0%> (-0.1%)	⬇️
flopy/utils/recarray_utils.py	94.4% <50.0%> (-5.6%)	⬇️

... and 7 files with indirect coverage changes

[langevin-usgs]

Looks good, @wpbonelli. Not sure how often these functions are used, so impact should be minimal. Noticed tests are still failing.

[wpbonelli]

thanks @langevin-usgs I think CI will fail until

• docs(mf6io): update .dfn files corresponding to similar change in mf6 #1956 merges, and
• model splitter is modified for compatibility with the feature ID refactor @emorway-usgs is working on

[langevin-usgs]

Okay, thanks @wpbonelli. Hopefully @emorway-usgs can get that straightened out soon so we can merge.