GeneformerTokenizer updates

[mlin]

Updating our GeneformerTokenizer with features newly added upstream.

[codecov]

Codecov Report

Attention: Patch coverage is 43.47826% with 13 lines in your changes missing coverage. Please review.

Project coverage is 90.93%. Comparing base (fc0281b) to head (9b2bcd3).

❗ Current head 9b2bcd3 differs from pull request most recent head 4b996f8

Please upload reports for the commit 4b996f8 to get more accurate results.

Files	Patch %	Lines
...xperimental/ml/huggingface/geneformer_tokenizer.py	43.47%	13 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1199      +/-   ##
==========================================
- Coverage   91.11%   90.93%   -0.19%     
==========================================
  Files          77       77              
  Lines        5922     5944      +22     
==========================================
+ Hits         5396     5405       +9     
- Misses        526      539      +13     

Flag	Coverage Δ
unittests	90.93% <43.47%> (-0.19%)	⬇️

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