Add support for TOX_LIMITED_SHEBANG

[gaborbernat]

Resolves #2208.

[codecov]

Codecov Report

Merging #2226 (dc97d87) into rewrite (5ce5812) will decrease coverage by 0.00%.
The diff coverage is 98.52%.

@@             Coverage Diff             @@
##           rewrite    #2226      +/-   ##
===========================================
- Coverage    99.86%   99.85%   -0.01%     
===========================================
  Files          162      164       +2     
  Lines         9473     9538      +65     
  Branches       970      975       +5     
===========================================
+ Hits          9460     9524      +64     
  Misses           3        3              
- Partials        10       11       +1     

Flag	Coverage Δ
tests	99.85% <98.52%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
.../execute/local_subprocess/test_local_subprocess.py	99.55% <96.42%> (-0.45%)	⬇️
src/tox/execute/local_sub_process/__init__.py	95.80% <100.00%> (+0.15%)	⬆️
src/tox/execute/util.py	100.00% <100.00%> (ø)
...ests/execute/local_subprocess/test_execute_util.py	100.00% <100.00%> (ø)

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