feat: support binary & float vectors for IVF_FLAT index

[BubbleCal]

this splits the flat storage & distance calculator to float/int ones to support binary vectors.
merge them back after we figure out a generic way to handle both of binary & float vectors

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 17.14286% with 203 lines in your changes missing coverage. Please review.

Project coverage is 79.66%. Comparing base (8746737) to head (765ca49).
Report is 2 commits behind head on main.

Files	Patch %	Lines
rust/lance-index/src/vector/flat/storage.rs	20.00%	100 Missing ⚠️
rust/lance/src/index.rs	14.06%	0 Missing and 55 partials ⚠️
rust/lance-index/src/vector/flat/index.rs	0.00%	35 Missing ⚠️
rust/lance-index/src/vector/quantizer.rs	0.00%	5 Missing ⚠️
rust/lance/src/index/vector/ivf/v2.rs	0.00%	3 Missing ⚠️
rust/lance/src/index/vector/ivf.rs	0.00%	2 Missing ⚠️
rust/lance-index/src/vector/ivf.rs	0.00%	1 Missing ⚠️
rust/lance/src/index/vector/builder.rs	85.71%	0 Missing and 1 partial ⚠️
rust/lance/src/index/vector/ivf/io.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2461      +/-   ##
==========================================
- Coverage   79.99%   79.66%   -0.33%     
==========================================
  Files         207      207              
  Lines       58623    58888     +265     
  Branches    58623    58888     +265     
==========================================
+ Hits        46894    46916      +22     
- Misses       8970     9160     +190     
- Partials     2759     2812      +53     

Flag	Coverage Δ
unittests	79.66% <17.14%> (-0.33%)	⬇️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[BubbleCal]

move to #3198