DM-33528: Use importlib.resources rather than deprecated pkg_resources

[timj]

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.15 🎉

Comparison is base (454f83d) 85.74% compared to head (763275f) 85.89%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #55      +/-   ##
==========================================
+ Coverage   85.74%   85.89%   +0.15%     
==========================================
  Files          27       27              
  Lines        3838     3879      +41     
  Branches      791      800       +9     
==========================================
+ Hits         3291     3332      +41     
  Misses        428      428              
  Partials      119      119              

Impacted Files	Coverage Δ
python/lsst/resources/packageresource.py	100.00% <100.00%> (ø)
tests/test_resource.py	100.00% <100.00%> (ø)

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.