Enable using MLOps guidance in nested stack

[athewsey]

Issue #, if available: N/A

I'd like to be able to re-use the ml_ops solution guidance stack within other stacks: A deployable stack that provisions the dependencies, the guidance stack, and then some other resources e.g. a customised end-to-end state machine using the pre-built components.

Today, that's a challenge because the stacks don't expose any outputs. There's no config in AWS::CloudFormation::Stack to explicitly set stack name: It gets generated automatically and isn't visible via GetAtt on the resource either. So just locating resources by assumed name from the StackName isn't practical.

Description of changes:

To make building stacks that nest this guidance practical, proposing these updates:

• Expose useful outputs from MLOps solution guidance stack, including state machine ARNs and the final AWS Stack Name.
• Shorten role name that was causing problems when nesting the stack (64 character limit).
• Explicitly set string types to ambiguous bool parameters (YAML interprets plain true as a bool, not string, and in one instance I got errors during CFn deployment complaining about string types).
• Fill in a SFn description that was previously just placeholder.

Now, by nesting the solution in a parent stack something like this:

  PipelineStack:
    Type: 'AWS::CloudFormation::Stack'
    DependsOn:
      - DependencyStack
    Properties:
      Parameters:
        # DatasetIncludeRTS: true/false  - and other parameters etc.
        DatasetGroupName: forecast_e2e_demo
        SNSEndpoint: !Ref SNSEndpoint
        S3Bucket: !Ref S3Bucket
      TemplateURL: https://s3.amazonaws.com/doc-example-bucket/forecast-mlops-solution-guidance.yaml

...The parent stack can e.g. set up state machines referencing PipelineStack.Outputs.CreateDatasetGroupStateMachineArn, and use PipelineStack.Outputs.StackName if necessary.

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