Update on "Update QAT READMEs using new APIs"

Add references to new QAT APIs including `quantize_`,
`FakeQuantizedX`, and the new embedding Quantizers and
ComposableQATQuantizer. Also link to new QAT + LoRA recipe
in torchtune.

[ghstack-poisoned]

torchao/quantization/qat/__init__.py

@@ -1,8 +1,8 @@
 from .api import (
     ComposableQATQuantizer,
     FakeQuantizeConfig,
-    intx_quantization_aware_training,
     from_intx_quantization_aware_training,
+    intx_quantization_aware_training,
 )
 from .embedding import (
     Int4WeightOnlyEmbeddingQATQuantizer,