Backport PR #2048 on branch 0.12.x ((chore): Re-introduce strict warnings)

[meeseeksmachine]

Backport PR #2048: (chore): Re-introduce strict warnings

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.55%. Comparing base (29f394f) to head (fed1ec2).
⚠️ Report is 29 commits behind head on 0.12.x.

Files with missing lines	Patch %	Lines
src/anndata/_io/read.py	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           0.12.x    #2055      +/-   ##
==========================================
- Coverage   86.78%   85.55%   -1.23%     
==========================================
  Files          46       46              
  Lines        7076     7049      -27     
==========================================
- Hits         6141     6031     -110     
- Misses        935     1018      +83     

Files with missing lines	Coverage Δ
src/anndata/_io/specs/methods.py	90.16% <100.00%> (-0.90%)	⬇️
src/anndata/_io/read.py	81.95% <60.00%> (ø)

... and 12 files with indirect coverage changes