carto/protobuf @ v3.12.3

Joshua Haberman b971243fe0 Merge branch '3.12.x' into merge-release-branch		5 lat temu
..
src	0a737d8eb0 Sync from Piper @313142438	5 lat temu
BUILD	6bbd56dfd9 Bazel: Discontinue JDK 7 compatibility support	5 lat temu
generate-sources-build.xml	49efe9d7db Restructuring protobuf to multiple modules	9 lat temu
generate-test-sources-build.xml	cb390216cf Fixed the Java build.	5 lat temu
pom.xml	9ce8c330e7 Updated version to 3.12.3 and updated CHANGES.txt. (#7580)	5 lat temu