Create an explicit `QuantizationPreset` with flat preset options.
Create an explicit `QuantizationPreset` with flat preset options.

`QuantizationPreset` is the primary quantization configuration for the StableHLO Quantizer.
This message will cover most general quantization use cases, which can be overwritten with
`QuantizationConfig` (i.e. for selective quantization).

Follow up cl's will migrate the `QuantizationConfig` > `preset` usage from existing pipelines.
