perf: use the file metadata cache in scalar indices

[westonpace]

We were not using the cache before which meant every scalar index query had to load a bunch of metadata from the index files (some of which was quite expensive)

Closes #2313

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 93.33333% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 80.66%. Comparing base (b61850b) to head (08d6be9).

Files	Patch %	Lines
rust/lance-core/src/cache.rs	0.00%	0 Missing and 1 partial ⚠️
rust/lance-index/src/scalar/lance_format.rs	94.11%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2330      +/-   ##
==========================================
+ Coverage   80.64%   80.66%   +0.01%     
==========================================
  Files         192      192              
  Lines       56684    56699      +15     
  Branches    56684    56699      +15     
==========================================
+ Hits        45712    45735      +23     
+ Misses       8405     8395      -10     
- Partials     2567     2569       +2     

Flag	Coverage Δ
unittests	80.66% <93.33%> (+0.01%)	⬆️

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.