Just a tracking issue

• There are some CSR-related things @bkmartinjr can accelerate in Python
• @gspowley mentioned maybe we can do this in libtiledbsoma C++
• Or maybe even in TileDB core

This is a follow-on for #719, in case we need C++ work as well

Also, while single-cell-data/SOMA#83 is fabulous, we may wish to incorporate that logic into tiledbsoma.io's to_anndata/to_h5ad as well.

cc @aaronwolen

This should also support CSC, for R ecosystem benefit

Parent: #922

Internal tracking: [sc-31074]