feat: cxg conversion script updates for uns

[kaloster]

Reason for Change

• [2Q2024] Update CXG conversion script [previously - Change cxg conversion script to include uns data] #6659

Changes

• Added logic to extract uns dictionary from AnnData and store object under uns directory in the cxg
• Cast in_tissue column values to boolean to make it categorical, and fix the issue of it appearing as "continuous" in explorer
• Added unit test coverage

Testing steps

run def make_cxg() in a notebook or from the command line against a valid AnnData/h5ad dataset.
run converted cxg in explorer, verify spatial mode

Notes for Reviewer

[codecov]

Codecov Report

Attention: Patch coverage is 94.73684% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 91.65%. Comparing base (698cfc9) to head (0cd25da).

Files	Patch %	Lines
backend/common/utils/cxg_generation_utils.py	89.47%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6904   +/-   ##
=======================================
  Coverage   91.65%   91.65%           
=======================================
  Files         182      183    +1     
  Lines       15354    15390   +36     
=======================================
+ Hits        14072    14106   +34     
- Misses       1282     1284    +2     

Flag	Coverage Δ
unittests	91.65% <94.73%> (+<0.01%)	⬆️

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