add transcribe_asr extension; optimize bedrock_llm extension; fix polly_tts bugs

[Chen188]

Amazon Transcribe ASR Extension

Configurations

You can config this extension by providing following environments:

Env	Required	Default	Notes
AWS_REGION	No	us-east-1	The Region of Amazon Transcribe service you want to use.
AWS_ACCESS_KEY_ID	No	-	Access Key of your IAM User, make sure you've set proper permissions to start stream transcription. Will use default credentials provider if not provided. Check document.
AWS_SECRET_ACCESS_KEY	No	-	Secret Key of your IAM User. Will use default credentials provider if not provided. Check document.