Add State Property to Schedule EventSource in StateMachine

[konoui]

Describe your idea/feature/enhancement

AWS::Serverless::StateMachine should support State property for Schedule EventSource as well as AWS::Serverless::Function does #1329.
#1666 does not fix AWS::Serverless::StateMachine.

Proposal

We would like to use conditional logic for schedule event.

Resources:
  StateMachine:
    Type: AWS::Serverless::StateMachine
    Properties:
      (snip)
      Events:
        Schedule:
          Type: Schedule
          Properties:
            Schedule: rate(1 minute)
            State:
              Fn::If:
              - IsDev
              - DISABLED
              - ENABLED

Additional Details

[jfuss]

Thanks for the report and PR. Will follow up on a review by end of week.