Add sort parameter to points model

[LucaMarconato]

In spatialdata-io (e.g. in xenium()) we generally want the sort=True, here I enable this via a parameter.

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 91.82%. Comparing base (2e1347d) to head (a2aab25).
Report is 28 commits behind head on main.

Files with missing lines	Patch %	Lines
src/spatialdata/models/models.py	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #672      +/-   ##
==========================================
- Coverage   91.83%   91.82%   -0.02%     
==========================================
  Files          44       44              
  Lines        6776     6779       +3     
==========================================
+ Hits         6223     6225       +2     
- Misses        553      554       +1     

Files with missing lines	Coverage Δ
src/spatialdata/models/models.py	87.55% <87.50%> (-0.14%)	⬇️

[LucaMarconato]

The test that fails is unrelated to this PR.