feat(efs): Add support for specifying the EFS throughput mode

[bdmartin]

• Add support for specifying the EFS throughput mode (and the provisioned throughput if/when PROVISIONED throughput mode is chosen)
  • Updated unit tests to cover new functionality
  • Updated existing unit test to pass for IAM related changes
• Update the documentation
• Upgrade the cdk lib to 2.54.0 as that is when the ELASTIC throughput mode was added: https://github.com/aws/aws-cdk/releases/tag/v2.54.0

This fixes: https://github.com/awslabs/cdk-serverless-clamscan/issues/1261

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[bdmartin]

@dontirun - What do you think of this change? Is there anything you'd like me to change about it?

[bdmartin]

Thanks for the PR! Should be good to go after this small change

Done. Thank you!

[dontirun]

@bdmartin You'll need to run the npx projen build command locally and push the documentation changes.