feat: new cache methods: hardlink and symlink_individual

[frostming]

Signed-off-by: Frost Ming me@frostming.com

Pull Request Checklist

• 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.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (29311ba) 84.35% compared to head (75108cb) 84.49%.

Files	Patch %	Lines
src/pdm/utils.py	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #2425      +/-   ##
==========================================
+ Coverage   84.35%   84.49%   +0.13%     
==========================================
  Files         104      104              
  Lines       10227    10241      +14     
  Branches     2241     2244       +3     
==========================================
+ Hits         8627     8653      +26     
+ Misses       1121     1115       -6     
+ Partials      479      473       -6     

Flag	Coverage Δ
unittests	84.28% <96.96%> (+0.13%)	⬆️

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