This gives internal its own res directory, and pushes the build files down into
the source directory (as it is with all our other non-widget packages). Ideally
new things don't really get added to this package (instead they can be added to
feature/component-specific packages as package private). A few new packages had
to be created in order to break circular dependencies between widget and
internal.
This commit also fixes a number of problems with the Gradle build, as they were
mostly related to dependency issues or things not being included in
settings.gradle.
The next step here is to do the same for the widget package, and turn the lib
build files into something that just exports the other library packages.
PiperOrigin-RevId: 179866428
