[python] Ingest somacore classes

[ryan-williams]

Accompanying SOMA "core" changes: single-cell-data/SOMA#244

It can be awkward having some implementations in that repo:

• I'm experimenting with a dask kwarg to ExperimentAxisQuery.to_anndata; EAQ impl has lived in the core repo, to date, but arguably should not
• @bkmartinjr has been working on improved "fast CSR" algorithms, which were previously implemented and used in the SOMA core repo, but arguably belong in an implementation repo like this one.

Changes:
Move files and classes from single-cell-data/SOMA to this repo:

• _query.py:
  • Axis
  • AxisIndexer
  • AxisQueryResult
  • ExperimentAxisQuery
  • MatrixAxisQuery
  • JoinIDCache
• _fast_csr.py
• _eager_iter.py

[codecov]

Codecov Report

Attention: Patch coverage is 88.33333% with 56 lines in your changes missing coverage. Please review.

Project coverage is 85.73%. Comparing base (33b104c) to head (9b5366f).
Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3307      +/-   ##
==========================================
+ Coverage   85.29%   85.73%   +0.43%     
==========================================
  Files          52       55       +3     
  Lines        5517     5980     +463     
==========================================
+ Hits         4706     5127     +421     
- Misses        811      853      +42     

Flag	Coverage Δ
python	85.73% <88.33%> (+0.43%)	⬆️

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Components	Coverage Δ
python_api	85.73% <88.23%> (+0.43%)	⬆️
libtiledbsoma	∅ <ø> (∅)