Use case

Fuchsia has renamed the component ime_service.cmx to text_manager way back when.
We kept the old component because of external code, such as flutter-embedder-test2.cc, but
now it is time to retire the old component.

To do that, we must first migrate all uses of ime_service.cmx to the new component.

Proposal

I will send a pull request that makes the change.

For bug managers: please assign me to this issue.