CHORE: Update the build backend

[dipinknair]

This is to update the build backend from flit to pdm.

pdm offers packaging non python scripts.

Related to #1286

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.04% (target: -1.00%)	✅ ∅

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (f7ca120)	2619	2253	86.03%
Head commit (d7e59c6)	2619 (+0)	2254 (+1)	86.06% (+0.04%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#1285)	0	0	∅ (not applicable)

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.06%. Comparing base (f7ca120) to head (d7e59c6).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1285      +/-   ##
==========================================
+ Coverage   86.02%   86.06%   +0.03%     
==========================================
  Files          40       40              
  Lines        2619     2619              
==========================================
+ Hits         2253     2254       +1     
+ Misses        366      365       -1     

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