Persisting a new baseline on every push to master (which happens many
times a day) burns a full production build each time for no benefit a
once-a-day refresh doesn't already cover -- a day-old baseline is fine for
catching relative regressions on PRs. Moves baseline persistence to a new
frontend-bundle-size-nightly.yml (schedule + workflow_dispatch), and
restricts superset-frontend.yml's bundle-size job to pull_request only:
compare-and-alert against the last nightly baseline, never persist.
Also caches webpack's persistent filesystem build cache
(superset-frontend/.temp_cache) across CI runs via actions/cache, keyed on
the same files webpack's own `buildDependencies` invalidates on. Without
this, every PR run would pay the full cold-build cost (several minutes)
instead of the ~20s warm-build cost the cache is supposed to buy --
GH-hosted runners are fresh VMs with nothing carried over between jobs, so
the cache has to be restored explicitly or it does nothing.
f7e29c15d5