Remove distlib monkeypatches

[gaborbernat]

Adapt the new features added in distlib instead.

[codecov]

Codecov Report

Merging #1880 into master will decrease coverage by 8.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1880      +/-   ##
==========================================
- Coverage   93.97%   85.96%   -8.02%     
==========================================
  Files          86       86              
  Lines        4184     4174      -10     
==========================================
- Hits         3932     3588     -344     
- Misses        252      586     +334     

Flag	Coverage Δ
#tests	85.96% <100.00%> (-8.02%)	⬇️

Impacted Files	Coverage Δ
...ualenv/seed/embed/via_app_data/pip_install/base.py	98.31% <100.00%> (-0.14%)	⬇️
src/virtualenv/util/subprocess/_win_subprocess.py	0.00% <0.00%> (-95.09%)	⬇️
src/virtualenv/util/path/_pathlib/via_os_path.py	0.00% <0.00%> (-91.35%)	⬇️
...nv/create/via_global_ref/builtin/cpython/mac_os.py	24.44% <0.00%> (-59.45%)	⬇️
...ualenv/create/via_global_ref/builtin/pypy/pypy2.py	58.44% <0.00%> (-40.26%)	⬇️
src/virtualenv/util/__init__.py	83.33% <0.00%> (-16.67%)	⬇️
src/virtualenv/util/path/_pathlib/__init__.py	29.16% <0.00%> (-12.51%)	⬇️
src/virtualenv/util/subprocess/__init__.py	88.88% <0.00%> (-11.12%)	⬇️
...nv/create/via_global_ref/builtin/cpython/common.py	92.10% <0.00%> (-7.90%)	⬇️
src/virtualenv/util/path/_sync.py	86.20% <0.00%> (-6.90%)	⬇️
... and 14 more

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