perf: parallelize indexing partitions

[BubbleCal]

parallelize v3 indexing partitions, this would improve indexing speed for IVF_PQ & IVF_FLAT on v3

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 85.59322% with 17 lines in your changes missing coverage. Please review.

Project coverage is 79.03%. Comparing base (bcb040e) to head (75da9e2).

Files with missing lines	Patch %	Lines
rust/lance/src/index/vector/builder.rs	85.59%	1 Missing and 16 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3303      +/-   ##
==========================================
+ Coverage   78.96%   79.03%   +0.07%     
==========================================
  Files         246      246              
  Lines       87589    87648      +59     
  Branches    87589    87648      +59     
==========================================
+ Hits        69164    69274     +110     
+ Misses      15558    15509      -49     
+ Partials     2867     2865       -2     

Flag	Coverage Δ
unittests	79.03% <85.59%> (+0.07%)	⬆️

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