Improve Linux ARM64 testing capabilities

[fweikert]

We've successfully migrated our Linux ARM64 workers to GCP (#2272), but currently we mostly build binaries on Linux ARM64 instead of running tests.

There are two blockers for more widespread use of this platform for testing:

1. Our current quota is only enough for ten workers in the Bazel org.
2. We only publish multi-platform Docker images for Rocky Linux 8 and Ubuntu 20.04, but there is demand for newer OS versions ([feat] Add ubuntu2204_arm64 and ubuntu2404_arm64 to CI bazel-central-registry#3680).