[MOD-10236] Add serialization to SVS index

[lerman25]

This PR refactors the serialization logic for vector indexes by introducing a clear abstraction layer via the Serializer base class. Both HNSWSerializer and SVSSerializer now inherit from this interface, enabling:

• Unified structure for save/load operations across index types
• Encoding version support for backward/forward compatibility
• Cleaner separation of shared vs. index-specific serialization logic
• Easier extension for future index types

Each index (e.g., HNSWIndex, SVSIndex) implements its own saveIndexFields method to handle template- and implementation-specific data.

---

This PR also introduces support for saving/loading SVS indexes and validating their internal consistency.
Specifically:

• Implements the Serializer interface for SVS, enabling saveIndex() and loadIndex() methods. (Using a commit created by @rfsaliev )
• Adds a checkIntegrity() method for runtime validation of index structure and metadata.

[CLAassistant]

All committers have signed the CLA.

[meiravgri]

Awesome!
main comments are regarding visibility :)
missing review for svs_extensions.h and svs_utils.h, will go over with @rfsaliev

[rfsaliev]

IMHO a lot of unnecessary code duplication.

[codecov]

Codecov Report

Attention: Patch coverage is 90.15152% with 39 lines in your changes missing coverage. Please review.

Project coverage is 96.54%. Comparing base (dca6041) to head (265d238).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/VecSim/algorithms/svs/svs_serializer_impl.h	78.84%	22 Missing ⚠️
src/VecSim/algorithms/hnsw/hnsw_serializer_impl.h	94.91%	9 Missing ⚠️
src/VecSim/algorithms/svs/svs_serializer.h	45.45%	6 Missing ⚠️
src/VecSim/algorithms/svs/svs_serializer.cpp	95.00%	1 Missing ⚠️
src/VecSim/index_factories/svs_factory.cpp	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #716      +/-   ##
==========================================
- Coverage   96.84%   96.54%   -0.31%     
==========================================
  Files         122      125       +3     
  Lines        7393     7578     +185     
==========================================
+ Hits         7160     7316     +156     
- Misses        233      262      +29     

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[meiravgri]

Great work!!!
Had a few comments :)
Also, we need to implment a complemantry logic to serialize SVSIndex from the tiered index, and a tiered index ctor that will recieve an svs index loaded from disk
But IMO should be done in a seperate PR.