fix: Fix the support for relative paths from outside the project

[frostming]

Pull Request Check List

• A news fragment is added in news/ describing what is new.
• Test cases added for changed code.

Describe what you have changed in this PR.

• Resolve Failure of Editable Installs from Relative Paths outside Project Root #1381
• Resolve Using relative path fails for commands with --project argument #1220
• Related to Local dependency and packaging #464

[codecov-commenter]

Codecov Report

Base: 84.94% // Head: 84.92% // Decreases project coverage by -0.02% ⚠️

Coverage data is based on head (1700a3b) compared to base (901c5e2).
Patch coverage: 93.61% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1432      +/-   ##
==========================================
- Coverage   84.94%   84.92%   -0.03%     
==========================================
  Files          88       88              
  Lines        7605     7620      +15     
  Branches     1777     1784       +7     
==========================================
+ Hits         6460     6471      +11     
- Misses        762      765       +3     
- Partials      383      384       +1     

Flag	Coverage Δ
unittests	84.73% <93.61%> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/pdm/models/requirements.py	94.73% <86.66%> (-0.48%)	⬇️
src/pdm/models/repositories.py	78.04% <92.85%> (+0.08%)	⬆️
src/pdm/cli/actions.py	80.27% <100.00%> (+0.13%)	⬆️
src/pdm/models/candidates.py	87.61% <100.00%> (+0.03%)	⬆️
src/pdm/project/core.py	89.20% <100.00%> (ø)
src/pdm/models/caches.py	87.71% <0.00%> (-1.17%)	⬇️

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