[ci-stats] move shipper to a package, validate limits in on-merge job (#149474)

We just had an issue where two PRs were merged and it caused the limit
of the `triggerActionsUi` bundle to be exceeded, breaking PR builds. The
issue is that we didn't see any indication of this in the on-merge jobs
because we don't produce the PR report for on-merge jobs or ask ci-stats
if we should fail the job. Instead, we just ship the metrics for
baseline purposes. This fixes that problem by adding a `--validate` flag
to `node scripts/ship_ci_stats`, which takes care of sending at least
some ci-stats and will verify that the bundle limits are not exceeded.

Since we didn't catch this issue in the on-merge job the limits were
incorrect for over an hour and merged into many PRs, wasting engineering
and CI time.

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

scripts/ship_ci_stats.js

@@ -7,4 +7,4 @@
  */
 
 require('../src/setup_node_env');
-require('@kbn/dev-utils').shipCiStatsCli();
+require('@kbn/ci-stats-shipper-cli');