[text analytics] test issues #11442
Description
- switch instances of TextDocumentInput in tests for LD to DetectLanguageInput: https://github.com/Azure/azure-sdk-for-python/blob/feature/text_analytics_v3.0/sdk/textanalytics/azure-ai-textanalytics/tests/test_detect_language.py#L62
- service has fixed, remove skip: https://github.com/Azure/azure-sdk-for-python/blob/feature/text_analytics_v3.0/sdk/textanalytics/azure-ai-textanalytics/tests/test_detect_language.py#L516
- add test for client with null endpoint
- pass in invalid language to appropriate endpoints
- pass in null for docs to all endpoints
- make sure elements returned in same order
- make sure inner error takes precedence over outer error
- remove duplicate bad_model_version tests