Optimize Bundle Size

Use this workflow to keep limits stable by moving non-critical code out of the entry bundle.

1) Set a baseline

1. Reference docs/extend/ci-metrics.md for metric definitions and limits workflow details.
2. Build dist metrics for the target plugin and record current page load bundle size.

node scripts/build_kibana_platform_plugins --focus <pluginId> --dist --workers 4
cat <pluginDir>/target/public/metrics.json

3. If this is a regression investigation, compare plugin limits on branch vs upstream.