Add IME action to Enter editor action

At the moment apps need to support pressing "Enter" to search
differently if they want to support physical keyboard, as
currently no editor action is sent from it. This is a proposal
that will resolve that issue by sending that information.

Bug: 269672396
Test: built, flashed on device, confirmed pressing enter starts
the search

Change-Id: I1694303540295603097db2fd4e4206f1ca71cec0