Revert "bom: Remove protoc-gen-grpc-java"
Revert "bom: Remove protoc-gen-grpc-java"

This reverts commit 4a84c6fa96f11eababb32ab691e3bf9b62c3d374. The BOM
was usable for protoc-gen-grpc-java using dependencyManagement for the
buildscript. See conversation on #9020.

grpc/grpc-java,grpc/grpc-java,ejona86/grpc-java,ejona86/grpc-java,stanley-cheung/grpc-java,grpc/grpc-java,ejona86/grpc-java,stanley-cheung/grpc-java,grpc/grpc-java,stanley-cheung/grpc-java,stanley-cheung/grpc-java,ejona86/grpc-java