Handle invalid AWS profile gracefully instead of fatal exception

[himani2411]

Description of changes

When AWS_PROFILE is set to a non-existent profile, CLI commands using the @configure_aws_region() decorator (e.g. list-clusters, describe-cluster, list-official-images) raised an opaque "Unexpected fatal exception" message.

Catch botocore.exceptions.ProfileNotFound in _set_region(), configure_aws_region(), and configure_aws_region_from_config() and surface it as a BadRequestException with the actual error message.

This applies to all code paths: when --region is omitted (boto3.Session() fails in the decorator) and when --region is provided (boto3.Session() fails inside retrieve_supported_regions())

Tests

• Local tests

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