[FormRecognizer] v2.0 and v2.1 model training without labels is hanging

[kinelski]

A service issue that affects both Form Recognizer 2.0 and 2.1. Many tests and samples had to be disabled to unblock our live tests pipeline.

When the issue is fixed on the service side, affected tests and samples should be enabled again.

All affected tests and samples have been annotated with the following string to facilitate searching:

https://github.com/Azure/azure-sdk-for-net/issues/47689