Prefer setuptools imports to distutils imports

[akx]

Considering distutils is being deprecated, this fixes up things so imports from setuptools are used where available instead.

The non-conditional imports have been around for 6 to 17 years, so they should be safe in conservative situations too.

Refs #824

[codecov]

Codecov Report

Merging #843 (4f4ab10) into master (9033f02) will decrease coverage by 0.13%.
The diff coverage is 47.50%.

@@            Coverage Diff             @@
##           master     #843      +/-   ##
==========================================
- Coverage   91.16%   91.02%   -0.14%     
==========================================
  Files          23       23              
  Lines        4152     4158       +6     
==========================================
  Hits         3785     3785              
- Misses        367      373       +6     

Impacted Files	Coverage Δ
babel/messages/plurals.py	100.00% <ø> (ø)
babel/messages/frontend.py	86.10% <43.24%> (-0.94%)	⬇️
babel/messages/catalog.py	95.29% <100.00%> (-0.04%)	⬇️
babel/support.py	83.66% <100.00%> (ø)

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[akx]

For people working around e.g. Fedora packaging (@FelixSchwarz, @kloczek?), do you foresee this change causing trouble?

[FelixSchwarz]

Fedora has setuptools available so I don't think this will be an issue. In general Fedora seems to be pretty much at the (b)leading edge of Python versioning so if something is deprecated upstream, chances are pretty good that Fedora's Python packaging (in general) was already adapted to support the new approach.