Clean check-in of AI/ML. Supersedes #948.

[stevespringett]

This PR supersedes #948, which introduced a number of unnecessary changed files and originated outside of the specification repo.

[stevespringett]

There are multiple things that are currently broken with #948 that this PR will attempt to resolve. This includes references to objects that no longer exist in 2.0, improper use of objects in 2.0, and lack of integration with the component model. This PR will also introduce the required test fixtures (valid / invalid) necessary for the RFC period.

[JunHwan-Kwon]

Thanks for moving the AI/ML work into a clean in-repository branch.

The tensor-level affine quantization gap I raised on #948 still seems to apply here. modelParameter.format is additionalProperties: false and defines dataType, encoding, and mimeType, with no typed representation for scale values, zero-points, or quantization axes. modelParameter.properties can hold those as strings, but the schema cannot validate a per-axis scale vector or check its cardinality against the corresponding tensor dimension.

The reproducible TFLite evidence, the ONNX correspondence (per-tensor, per-axis, and blocked granularity), and a proposed framework-neutral shape are all in that comment:
#948 (comment)

I understand that the draft is still being stabilized, so no response is needed at this stage. Once the structure and fixtures settle, I would be glad to help with the aligned JSON, XML, and protobuf definitions and the corresponding valid and invalid tests.