FR: Running the bazel tests with a custom configuration

The Java tools have been recently moved out of the bazel binary (see bazelbuild/bazel#6316) and are now released separately. However the Java tools need to maintain the same level of testing coverage as before. One idea is to introduce a new flag in Bazel that points to a Java tools archive and have a presubmit pipeline running all the bazel tests with the flag pointing to the Java tools archive built at head. Other ideas of keeping the same testing coverage are welcome.

cc: @fweikert