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.
This improves our documentation for the gradle protobuf plugin, as its
version is dependent on the gradle version.
Gradle now has the --tests flag, performance improvements, and support
for OpenPGP subkeys.
This fixes a problem where gradle would try to use VC's amd64_x86 cl
(without the correct environment) and fail to compile with return code
-1073741515 (STATU_DLL_NOT_FOUND) because of missing mspdb120.dll.