Add actions to modify createdAt for debugging

[jonalmeida]

In Fenix, we want need a way to make specific tabs "inactive" for demoing and testing purposes and requires us to modify the lastAccess and createdAt properties. We also do not want these actions to be used in error and make it obvious to the user that these are not meant for end-users.

The proposal is to add a set of DebugAction that can modify internal state and, in the future, have the ability to add other useful debug actions.

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