Android Gradle plugin bumped to 4.2.0 in examples, for Gradle 7 compat
and to match main build.
Jib 3 changed default base image away from distroless, but we do want
to use distroless.
The examples are no longer part of the normal build, although they are
built with Travis. The examples now include their own copy of the gradle
wrapper to ease usage from IDEs which can now properly detect the
correct version of gradle to use.
The build files were generated using "gradle init" and "mvn
archetype:generate" and then modified following our README.
Fixes#1414
Eric Anderson