Simplified affine matrix calculation for datashader

[timtreis]

Original PR here: #424 by @LucaMarconato

but rebasing was too much of a PITA

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.89%. Comparing base (31b1ee3) to head (294706a).
⚠️ Report is 33 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #491      +/-   ##
==========================================
- Coverage   84.08%   83.89%   -0.20%     
==========================================
  Files           8        8              
  Lines        1841     1819      -22     
==========================================
- Hits         1548     1526      -22     
  Misses        293      293              

Files with missing lines	Coverage Δ
src/spatialdata_plot/pl/render.py	91.50% <100.00%> (-0.02%)	⬇️
src/spatialdata_plot/pl/utils.py	77.94% <100.00%> (-0.43%)	⬇️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.