[Flock][Feature] - Publish IME connection status globally

[matthew-carroll]

Flutter Issue Ticket Link:
flutter/flutter#117771

Why didn't Flutter implement this?
Flutter team agreed this is a legitimate request. But it's been 2 years without it being done. Seems it's not a priority.

Why does this belong in Flock?
Only Flutter can control the IME. This problem can't be solved by a package or an app.

Describe the solution you'd like
I'd like to be able to query the IME connection status. I'd also like to be able to listen for connection status changes.

Additional context
This is a useful capability because some UI elements need to appear/disappear based on IME connection status. That behavior, right now, at best, requires spaghetti code so that UI code can dig into other areas that talk to the IME. Or, it requires watching indirect signals, like focus changes, and then using that to infer IME connection status, which has many edge cases and tends to produce bugs.