Refactor LISI metrics

[mumichae]

• remove computational bottlenecks
• start from harmonypy implementation for LISI TODO in new PR

[codecov]

Codecov Report

Attention: Patch coverage is 80.55556% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 57.97%. Comparing base (59ae6ee) to head (824c146).

❗ Current head 824c146 differs from pull request most recent head fa77b53. Consider uploading reports for the commit fa77b53 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #395      +/-   ##
==========================================
+ Coverage   52.81%   57.97%   +5.15%     
==========================================
  Files          22       22              
  Lines        1882     1675     -207     
==========================================
- Hits          994      971      -23     
+ Misses        888      704     -184     

Flag	Coverage Δ
unittests	57.97% <80.55%> (+5.15%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
scib/metrics/lisi.py	80.47% <80.55%> (+38.18%)	⬆️

[VladimirShitov]

I believe, there is a bug with n_batches atm, could you please check it? Otherwise, looks good :)