Add support for the AWS CDK CLI

We want to use the AWS CDK to generate our cloudformation templates.

This could be accomplished manually using a generic powershell task (given the CDK cli is installed) but the best thing (and the thing I like most about the plugin you've created) is the way it automatically pulls in credentials from our account. This makes handling the different credentials for our various AWS accounts and build environments SO much easier and makes key rotation a non issue for us.

The issue names no files or tests. Start by comparing the existing generic PowerShell task and AWS credential handling with the AWS CDK CLI workflow; done means an Azure DevOps task can invoke the installed CDK CLI to generate CloudFormation templates while using the plugin's account credentials.

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