We need to stop using maven repo on GCS to store artifacts for the
schema compatibility tests. After public access is removed from GCS
buckets, Kokoro won't be able to access it: normal access will be
denied, and the repo is too large to map (copy) to Kokoro VM as a
resource.
This PR uploads the relevant jars to each release's folder. See
go/dr-gcs-public-access-prevention for details.
Weimin Yu
d4a70c29a8