[builder] enable Arrow Dictionary feature flag

[bkmartinjr]

This PR enables the use of Arrow dictionary (aka TileDB enum, Pandas Categorical, ...) in building the Census. Affects various string columns in the obs dataframe which contain repetitive labels, such as cell_type. Primary impact is more efficient memory use for end-user (reader) of Census obs dataframe.

Fixes #604

Other changes:

• the ZStd compression level for the affected columns was reduced (the high setting had no significant value after this change).
• package dependencies were updated to latest
• Port to latest, non-deprecated, indexer in tiledbsoma

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 81.35%. Comparing base (a5dbdef) to head (d1dde47).

Files	Patch %	Lines
...llxgene_census_builder/build_soma/validate_soma.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1064      +/-   ##
==========================================
+ Coverage   81.33%   81.35%   +0.01%     
==========================================
  Files          73       73              
  Lines        5566     5566              
==========================================
+ Hits         4527     4528       +1     
+ Misses       1039     1038       -1     

Flag	Coverage Δ
unittests	81.35% <33.33%> (+0.01%)	⬆️

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[prathapsridharan]

LGTM