fix: fixes #10738 by adding function for scrubbing cross-regional pre…

[glorious-beard]

…fix from model id

If present, removes the "us.", "eu.", or "apac." preceding the model id when selecting the correct model service for the given model.

Motivation and Context

1. Why is this change required? This is to allow the use of cross-region inference models in the Amazon Bedrock connector.
2. What problem does it solve? This fixes a bug in BedrockServiceFactory.cs in which the cross-regional identifier in a model was getting treated as an LLM provider.
3. What scenario does it contribute to? Use of cross-regional inference models in Amazon Bedrock, namely Claude 3.7 Sonnet from a us-west-2 data center.
4. If it fixes an open issue, please link to the issue here.
   • .Net: Bug: AWS Bedrock Connector - Cross-region inference Not Supported microsoft/semantic-kernel#10738
   • .Net: New Feature: .NET support calling Inference profiles with AWS Bedrock microsoft/semantic-kernel#10047

Description

This is a minimal-change quick fix for enabling cross-regional models in Amazon Bedrock. It looks for one of the three standard cross-regional identifiers at the start of the model ID in the bedrock service factory, and if present, removes it. With the model ID stripped of the cross-region header, existing logic is used to select the correct LLM service.

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 😄