Disable VECTOR_INT8 for all index types except HNSW

[cydrain]

Issue: #977

[mergify]

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[cydrain]

/kind improvement

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.05%. Comparing base (3c46f4c) to head (164be76).
Report is 308 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##           main    #1059       +/-   ##
=========================================
+ Coverage      0   72.05%   +72.05%     
=========================================
  Files         0       86       +86     
  Lines         0     8196     +8196     
=========================================
+ Hits          0     5906     +5906     
- Misses        0     2290     +2290     

see 86 files with indirect coverage changes

[foxspy]

/lgtm

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