CWE rules with multiple policy targets (instead of 1:1 ratio of rules to lambda/policies) - parallel execution

[FireballDWF]

Enhance the mu.py deployer to detect when there is an existing CWE with the same exact event name/source/ids and if so then add the additional target rather than current behavior of creating a new rule. CWE invokes multiple targets in parallel.

Benefits:

1. AWS CloudWatch events service team has previously asked for this behavior in response to requests for limit increase from the default limit of 100 rules as it helps scalability.
2. Reduces the need for customers to request this limit increase, and the associated waiting period for the limit increase to be put into effect if/when they hit the limit before realizing this limit even exists.

[FireballDWF]

For now consider this low priority.