[Errors] Improve error messages where service message is unclear

[annelo-msft]

Case	Error Message	Suggested Improvement
Pass useTrainingLabels=true when no labels are in blob storage	{             code: '2100',             message: "Can't find any OCR files for training."           }	Teams Discussion
Pass local filepath to RecognizeXxFromUri method	Status: 400 (Bad Request) Content: {"error":{"code":"1003","message":"Parameter 'Source' is not a valid Uri."}} From https://stackoverflow.com/questions/62043368/startrecognizecustomformsfromuri-returns-parameter-source-is-not-a-valid-uri	See Teams Discussion
Make sure that GetModelIdAsync returns a sensible error in the event that an account limit is exceeded (issue #11462)	-- Need to check	--

Another one to look at https://github.com/Azure/azure-sdk-for-net/issues/12813

[maririos]

Pass useTrainingLabels=true when no labels are in blob storage

Issue https://msazure.visualstudio.com/Cognitive%20Services/_workitems/edit/7310258 filed for service team to improve the message.

Pass local filepath to RecognizeXxFromUri method

Pinged service team to see if they can improve the error mesage.

Make sure that GetModelIdAsync returns a sensible error in the event that an account limit is exceeded

Error message is enough. {"error":{"code":"1014","message":"The model count for the subscription has exceeded limit. Delete old models before creating new ones."}}

AAD Token against a region endpoint.

Asking the service team

[maririos]

Pass local filepath to RecognizeXxFromUri method

Issue https://msazure.visualstudio.com/DefaultCollection/Cognitive%20Services/_workitems/edit/7587655/

AAD Token against a region endpoint.

Following up on issue #12813