refactor: turbo quantizer

[richyreachy]

This PR introduces a pluggable Quantizer abstraction in the Turbo module and provides the first concrete implementation along with scalar fp32 distance kernels.

The goal is to establish a uniform interface that future quantizers (int8 uniform, int8 record, PQ, RaBitQ, …) can implement, decoupling quantization logic from index builders and searchers.

As parts of the initial concept introduction of Turbo, the inclusive changes are as follows:

1. New Quantizer abstract base class
2. DistanceImpl callable distance handle
3. Fp32Quantizer first concrete implementation
4. Scalar Fp32 distance kernels
5. IndexMeta and IndexQueryMeta extensions
6. IndexFactory quantizer support