Remove numpy dependencies in src/lightning/pytorch

[Peiffap]

What does this PR do?

Removes dependency on numpy in part of the codebase (src/lightning/pytorch), as mentioned in #17278.

Partially fixes #17278

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📚 Documentation preview 📚: https://pytorch-lightning--19841.org.readthedocs.build/en/19841/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 53%. Comparing base (fd86ea7) to head (737fda6).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #19841      +/-   ##
==========================================
- Coverage      84%      53%     -31%     
==========================================
  Files         426      418       -8     
  Lines       35256    35103     -153     
==========================================
- Hits        29679    18695   -10984     
- Misses       5577    16408   +10831     

[awaelchli]

Thanks a lot for your recent PRs @Peiffap!