`elastic-package export` should work with any asset that packages can include

This would be a nice QoL addition since there are many assets other than dashboards and pipelines that packages can include.

Extending the export command to support them would be very helpful to prevent errors and for a better experience.

Start with the `elastic-package export` command and inspect how it currently handles dashboards and pipelines. Identify the other asset types that packages can include and define completion as exporting each supported asset without errors; the issue does not name specific files or tests.

Written by the indexing model from the issue text.