[ci] Migrate Turbopack build_and_test jobs back to arm64, leave webpack jobs as x86-64 (#95374)
IT increased the concurrency limit from 50 to 100. This ramps back up
the `build_and_test` job. I'll keep an eye out for long queue times
before migrating us all the way back to arm64.
https://vercel.slack.com/archives/C0B0LKK5QD7/p1782910263667649?thread_ts=1782838752.523649&cid=C0B0LKK5QD7