feat(sample): update contract compliance deps and enable Amazon Nova model support

[krokoko]

Issue #, if available:

Description of changes:

• Update the python dependencies
• Update permissions to invoke any foundation model from Amazon Bedrock, as well as to enable inference profiles
• Update code to parse correctly the response metadata and response when using a different model (Amazon Nova)
• Update documentation to add guidance on how to use a different model
• Remove the deprecated langchain_dep_layer from gen ai cdk constructs
• Remove guidance requiring to add a Docker flag since the sample is now using the PythonLayerVersion from the aws_lambda_python_alpha package, which manages correctly the platform

Testing:

Deployed and ran both the existing default model, and Amazon Nova Pro v1

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