feat: add a fixer for deprecating cross platform strategy

[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: Patch coverage is 72.22222% with 5 lines in your changes missing coverage. Please review.

Project coverage is 85.27%. Comparing base (0097247) to head (65e0351).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/pdm/cli/commands/fix/fixers.py	68.75%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3259      +/-   ##
==========================================
- Coverage   85.30%   85.27%   -0.04%     
==========================================
  Files         112      112              
  Lines       11352    11368      +16     
  Branches     2473     2474       +1     
==========================================
+ Hits         9684     9694      +10     
- Misses       1140     1146       +6     
  Partials      528      528              

Flag	Coverage Δ
unittests	85.07% <72.22%> (-0.04%)	⬇️

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