AWS::EMR::Cluster - InstanceGroupConfig-managed scaling

Scope of request:
EMR has introduced a new way of autoscaling called "EMR Managed Scaling" (https://docs.aws.amazon.com/emr/latest/ManagementGuide/emr-managed-scaling.html) which is not yet available on CF
Here is the link to how to configure this via the CLI: https://docs.aws.amazon.com/emr/latest/ManagementGuide/managed-scaling-cli.html
It should include the configurable parameters (all required):
```
ComputeLimits
UnitType:
MinimumCapacityUnits:
MaximumCapacityUnits:
MaximumOnDemandCapacityUnits:
```

Expected behavior:
Maybe the option should be available even one level below on `AWS::EMR::Cluster AutoScalingPolicy` up to you guys to decide, but it should give the user the chance to opt-in on the managed scaling feature instead of defining a custom scaling policy

The console brings the possibility to switch between regular and managed scaling so probably this should be supported on update

Suggest specific test cases:
It should be mutually exclusive with the existing `AWS::EMR::Cluster AutoScalingPolicy`, it is either one or the other

Helpful Links to speed up research and evaluation:
https://docs.aws.amazon.com/emr/latest/ManagementGuide/emr-managed-scaling.html
https://docs.aws.amazon.com/emr/latest/ManagementGuide/managed-scaling-cli.html
https://aws.amazon.com/blogs/big-data/introducing-amazon-emr-managed-scaling-automatically-resize-clusters-to-lower-cost/

Category:
Analytics
(EMR)

Start with the linked EMR Managed Scaling documentation and CLI configuration guide, then inspect how AWS::EMR::Cluster currently exposes AutoScalingPolicy. Confirm the required ComputeLimits parameters, the mutual exclusivity and update behavior, and add coverage for switching between regular and managed scaling.

Written by the indexing model from the issue text.