Add support for FP16/INT8 on GPU indexes

[lowener]

This is a WIP. TODO: Add support for CAGRA+HNSW int8 issue: #1201

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[alexanderguzhva]

/lgtm

[alexanderguzhva]

issue #1201

[alexanderguzhva]

issue: #1201

[alexanderguzhva]

/kind improvement

[alexanderguzhva]

/approve

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