pgrep: implement -P/--parent

[cakebaker]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 90.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 57.40%. Comparing base (2cf8884) to head (66ede2a).
Report is 7 commits behind head on main.

Files	Patch %	Lines
src/uu/pgrep/src/pgrep.rs	80.00%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #144      +/-   ##
==========================================
+ Coverage   57.02%   57.40%   +0.37%     
==========================================
  Files          23       23              
  Lines        2897     2925      +28     
  Branches      452      458       +6     
==========================================
+ Hits         1652     1679      +27     
+ Misses       1099     1098       -1     
- Partials      146      148       +2     

Flag	Coverage Δ
macos_latest	44.52% <12.50%> (-0.13%)	⬇️
ubuntu_latest	54.78% <90.00%> (+0.34%)	⬆️
windows_latest	0.08% <0.00%> (-0.01%)	⬇️

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[Krysztal112233]

Thanks :)