Update the namespace for all examples

[rib]

Currently all the examples are under a co.realfit domain-based namespace, except that the cargo apk builds will use a default package = "com.foo.bar"

We should update this to something like rust.mobile and be consistent between Gradle and cargo apk builds

[MarijnS95]

And we should probably clean out all the commented cargo-apk package metadata in Cargo.toml that is currently unused, and/or switch to (or at least provide) xbuild's manifest.yaml.

[rib]

I wonder if you could provide an example xbuild config for na-mainloop in a draft PR? I'd be happy to replace the cargo apk metadata with an xbuild config if you think that would be better?

[MarijnS95]

@rib see #9, cargo-apk has a sensible default and so has xbuild.

[MarijnS95]

TLDR: We can support both without providing any configuration for either 😬