Python: removes AWS "us." region prefix from model id

[gtang31-te]

Motivation and Context

relates to this issue.

Description

The current implementation of bedrock_model_provider.py is hard coded to return the zeroth element when splitting model_id on (.) periods. However this will return an incorrect name for the provider when working with an inference profile since the model_id will contain the AWS region in the ID. For example, a model_id can be us.meta.llama3-XXX:0 and the call to_model_provider will incorrectly try to look for a us model. This error is thrown when we are selecting an LLM model using an AWS inference profile.

I have made a change to the to_model_provider class method in the bedrock_model_provider.py script that checks for a region prefix and then strips it. I have not tested this against all AWS regions.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄