[MOD-12346] Remove main-thread graph repair from SVS delete operations

[meiravgri]

Fix 1:

Consolidation during deleteVector() operations blocks the main thread significantly.
Benchmarks show ~20 seconds to delete 500 vectors from a 1M vector index.
This PR removes automatic consolidation, leaving cleanup to the GC process.

Fix 2:

Align indexSize and indexLabelCount with HNSW behaviour:
IndexSize = indexLabelCount + num_marked_deleted
indexLabelCount represents only valid vectors.
Note: Unlike hnsw, svs doesn't perform in-place deletion, so this logic also applies to svs in a non-tiered index context.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.66%. Comparing base (1a15b59) to head (3ae28cd).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #831      +/-   ##
==========================================
+ Coverage   96.63%   96.66%   +0.02%     
==========================================
  Files         126      126              
  Lines        7379     7374       -5     
==========================================
- Hits         7131     7128       -3     
+ Misses        248      246       -2     

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[alonre24]

Nice!