Supporting functional mock using task name during unit test

[jerryyanmj]

In a flow, a composable function can be used multiple times with unique names. This makes functional mock difficult because the functional mock can only be achieved based on route name. Enhance the functional mock based on name will make unit test possible for flows with multiple uses of a single composable function.

[acn-ericlaw]

The proposed feature is awesome. We will implement this in our next release.