[FEA] Reduce template parameters

[cjnolet]

Currently, there's a lot of template params that could easily become runtime parameter. Every template param causes the need to compile more instantiations. If we reduce template params, we will improve compile time and binary size.

• Pairwise distances distance metric arg
• ANN filter type (make polymorphic)
• Reduce CAGRA / CAGRA-Q templates (make more runtime hyper-params)

@tfeher @divyegala @achirkin @benfred please add to this list as opportunities arise.

[cjnolet]

• Remove Linkage template parameter from the single linkage internals