feat: Add cross-region inference support for Bedrock models (#535)

[chm10]

This commit introduces the initial setup for supporting cross-region inference in the Bedrock Chat application.

Issue #, if available:

535

Description of changes:

• Added is_region_supported_for_inference function in utils.py to check if a region supports inference.
• Modified get_bedrock_client function in utils.py to use cross-region inference if enabled and the region is supported.
• Updated get_model_id function in bedrock.py to use the base model ID for cross-region inference if enabled, the region is supported, and the model is included in CROSS_REGION_INFERENCE_MODELS. If any of these conditions are not met, it falls back to using the local model ID and logs a warning.
• Added enableBedrockCrossRegionInference option to cdk.json with the default value set to false.

These changes lay the foundation for enabling cross-region inference in the Bedrock Chat application. The feature can be enabled or disabled using the enableBedrockCrossRegionInference configuration option in cdk.json.

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[statefb]

@chm10 Due to high demand, I've taken the initiative to implement this feature myself (#583 ). However, I sincerely appreciate your efforts and willingness to tackle this! Thank you for your understanding.