use python>=3.10 typing conventions

[quentinblampey]

Since spatialdata requires python>=3.10, we can remove most of the from __future__ import annotations, and also remove all the old typings such as Union or Optional

This PR is low priority, as it's just a cleanup

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.36%. Comparing base (def2d3c) to head (2ed9dd9).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #968      +/-   ##
==========================================
- Coverage   92.39%   92.36%   -0.03%     
==========================================
  Files          48       48              
  Lines        7440     7416      -24     
==========================================
- Hits         6874     6850      -24     
  Misses        566      566              

Files with missing lines	Coverage Δ
src/spatialdata/__init__.py	96.42% <ø> (-0.13%)	⬇️
src/spatialdata/_core/_deepcopy.py	98.36% <ø> (-0.03%)	⬇️
src/spatialdata/_core/_elements.py	92.30% <ø> (-0.09%)	⬇️
src/spatialdata/_core/_utils.py	100.00% <ø> (ø)
src/spatialdata/_core/centroids.py	100.00% <ø> (ø)
src/spatialdata/_core/concatenate.py	92.00% <ø> (-0.07%)	⬇️
src/spatialdata/_core/data_extent.py	97.88% <ø> (-0.03%)	⬇️
src/spatialdata/_core/operations/aggregate.py	94.31% <100.00%> (-0.04%)	⬇️
src/spatialdata/_core/operations/map.py	98.79% <ø> (-0.02%)	⬇️
src/spatialdata/_core/operations/rasterize.py	90.03% <ø> (-0.04%)	⬇️
... and 19 more

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