feat: support delta merge for IVF_HNSW_SQ

[BubbleCal]

[BubbleCal]

this is not efficient because it just skipped the IVF & quantization training, the graph will be re-constructed. I will leave the optimization (reuse the existing graph) to the next PR

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 79.60199% with 82 lines in your changes are missing coverage. Please review.

Project coverage is 81.16%. Comparing base (444328e) to head (be504f4).

Files	Patch %	Lines
rust/lance/src/index/vector/ivf.rs	78.39%	26 Missing and 17 partials :warning:
rust/lance-index/src/vector/quantizer.rs	50.79%	30 Missing and 1 partial :warning:
rust/lance/src/index/vector/fixture_test.rs	0.00%	2 Missing :warning:
rust/lance/src/index/vector/pq.rs	0.00%	2 Missing :warning:
rust/lance/src/session/index_extension.rs	0.00%	2 Missing :warning:
rust/lance-index/src/vector/hnsw/builder.rs	66.66%	0 Missing and 1 partial :warning:
rust/lance/src/index/vector/ivf/io.rs	88.88%	0 Missing and 1 partial :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2132      +/-   ##
==========================================
+ Coverage   81.15%   81.16%   +0.01%     
==========================================
  Files         186      186              
  Lines       54163    54521     +358     
  Branches    54163    54521     +358     
==========================================
+ Hits        43954    44250     +296     
- Misses       7729     7776      +47     
- Partials     2480     2495      +15     

Flag	Coverage Δ
unittests	81.16% <79.60%> (+0.01%)	:arrow_up:

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