Improve phone feedback for Wear onboarding

[jpelgrom]

Summary

Improve the (perceived) responsiveness of onboarding a watch via the phone by showing a loading indicator after submitting to indicate it's doing something, and Snackbars for success/error.

On failure, sending the stacktrace over to the phone is also useful, for now I'm just printing to the log. Example:

2023-04-02 17:14:16.333 22245-22245 SettingsWearViewModel   io....stant.companion.android.debug  E  Watch was unable to register: java.lang.Exception
                                                                                                    	at io.homeassistant.companion.android.phone.PhoneSettingsListener$login$1.invokeSuspend(PhoneSettingsListener.kt:148)
                                                                                                    	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
                                                                                                    	at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
                                                                                                    	at android.os.Handler.handleCallback(Handler.java:938)
                                                                                                    	at android.os.Handler.dispatchMessage(Handler.java:99)
                                                                                                    	at android.os.Looper.loop(Looper.java:223)
                                                                                                    	at android.app.ActivityThread.main(ActivityThread.java:7651)
                                                                                                    	at java.lang.reflect.Method.invoke(Native Method)
                                                                                                    	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
                                                                                                    	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

Screenshots

Before (stable):

onboard-old.mp4

After (this PR):

onboard-new.mp4

Link to pull request in Documentation repository

n/a

Any other notes

Onboarding speed depends on the connection, sometimes it completes in less than a second while other times I'm waiting close to 10 seconds - obviously these improvements will be most interesting in the latter case.