add seperate tokenizer manager for fast fields

[PSeitz]

No description provided.

[codecov-commenter]

Codecov Report

Merging #2019 (029f769) into main (ba309e1) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##             main    #2019      +/-   ##
==========================================
- Coverage   94.42%   94.39%   -0.03%     
==========================================
  Files         319      319              
  Lines       59216    59142      -74     
==========================================
- Hits        55914    55830      -84     
- Misses       3302     3312      +10     

Impacted Files	Coverage Δ
src/schema/text_options.rs	95.87% <ø> (ø)
src/core/index.rs	87.14% <100.00%> (+0.23%)	⬆️
src/fastfield/mod.rs	100.00% <100.00%> (ø)
src/indexer/segment_writer.rs	97.78% <100.00%> (+<0.01%)	⬆️

... and 16 files with indirect coverage changes

[fulmicoton]

approved but can you align naming one way or another before merging?