Add guidance for updating bundled packages in Kibana

As of 8.2, Kibana ships some packages bundled in the Kibana release (see https://github.com/elastic/kibana/issues/112095). As part of the release process, the `fleet_packages.json` file in the Kibana repo needs to be updated prior to the final BC for a release version. Currently, this is a manual process, but some assistance in the elastic-package CLI would go a long way to help. We could do something simple for now or go one step further to automate this process.

### Give guidance on how to manually update
It would be helpful to add guidance to the `elastic-package publish` command to help package owners be sure to update this file in the Kibana repo, when appropriate. This should show after `elastic-package publish` succeeds for a package in the following list:
- apm, elastic_agent, fleet_server, synthetics, endpoint

We could show something like this in the stdout:
```
You have published a package that is bundled by Kibana. There are additional steps required to update this package in Kibana snapshot, BC, and release builds.

If this version should be shipped in the next BC or release, update https://github.com/elastic/kibana/blob//fleet_packages.json on the appropriate release branch.

If this version should be used in development for next snapshot builds, update
https://github.com/elastic/kibana/blob/main/fleet_packages.json
```

### Automate opening a PR

Even better would be to open a PR against the Kibana repo for these changes, including against the correct release branch. One issue is that I think this would require asking the package owner for the intended Stack release version on the CLI or maybe we could use the `constraint.kibana.version` to infer this.

Start at the elastic-package publish command and review how successful publishing messages are assembled. Add guidance for packages in the listed bundled-package set, including the Kibana snapshot and release-branch fleet_packages.json links, then verify the output after a successful publish.

Written by the indexing model from the issue text.