Move Int8DynamicActivationIntxWeightConfig out of experimental

[metascroy]

This PR moves Int8DynamicActivationIntxWeightConfig and its quantizer into torchao.quantization.quant_api (out of experimental). Int8DynamicActivationIntxWeightConfig is refactored to closely mirror Int8DynamicActivationInt4WeightConfig when weight_dtype=torch.int4, layout=QDQLayout().

Quantization in Int8DynamicActivationIntxWeightConfig is done with QDQLayout, and then packing is done separately with make_packed_linear_int8_dynamic_activation_intx_weight_tensor. This is to separate the quantization algorithm from the storage. Both the packed and QDQLayout quantize with the same algorithm, and this is made explicit.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/ao/1968

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❌ 2 New Failures

As of commit 4a421db with merge base df532f0 ():

NEW FAILURES - The following jobs have failed:

• Code Analysis with Ruff / build (3.9) (gh)
  Process completed with exit code 1.
• PR Label Check / Check PR Labels (gh)
  Process completed with exit code 1.

This comment was automatically generated by Dr. CI and updates every 15 minutes.