update test script for bazel

[codyoss]

Today we have a test.sh script that generates a handful of good test APIs that exercise our generator. Running protoc though is not how we actually generate client libraries today in Go -- that is done via Bazel. We should have a version of this test that runs the bazel targets for these APIs as that can catch other problems that just invoking protoc will not catch. This could even run just on release PRs if we wanted as this sort of integration will take much longer to run.