Introduce a NameResolver for Android's intent: URIs

[jdcormie]

Let grpc-binder clients find on-device services by implicit Intent target URI, lifting the need to hard code a server's package name.

Android aspects of this code have already been reviewed internally. See http://cs/symbol:AndroidIntentNameResolver

Design at: go/grpc-binder-service-discovery

[jdcormie]

@ejona86 Do you still want to take a look at this or should I proceed based on @kannanjgithub's approval?

[ejona86]

Let's give me the rest of today to take a look.

[ejona86]

maybeCreateAndDefaultRegister() is my biggest concern. The other things are smaller. The Status codes we do need to be careful about, though, but it is also an easy fix.

[ejona86]

These are some comments from Friday that I didn't have an opportunity to finish. We can leave UNIMPLEMENTED for the moment; I've added a discussion topic for cross-language discussion. The exception just needs added context.