BC Fix Stage 2 new DQ Linear Path (#1961)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/1961

This is part 1 of BC Breaking changes.

Here we update the schema to XN01. We are now serializing new models. The changes in serialization here removing the old dqlinear path (dq_datatype). And using a new dq linear datapath. Serializing inputs as dynamically quantized for fully connected inputs.

We also introduce two new tensor types: DynamicallyQuantized and QuantizedPerChannel2 (this is used for 4 bit channel wise quantization)

Reviewed By: digantdesai, kirklandsign

Differential Revision: D53454518

fbshipit-source-id: 18eb16d6232786ba0e7f5cd919d47954d09e3f9b