Enums in Contract Interfaces cannot be updated to Cadence 1.0

[dsainati1]

Issue to be solved

Enums were previously allowed in contract interfaces as a type requirement, but with the removal of type requirements they are no longer allowed to appear there. However, there is no current migration path for any old enums of this kind, as there are no enum interfaces to update them to, and the update validator does not allow the removal of a type declaration.

Suggested Solution

We should either allow enum declarations to be removed from contract interfaces (which should be safe because the enum will be declared in all contracts that conform to that interface) or come up with an alternative data migration to support this case.