Move the Welcome dashboard into the drupal_cms_admin_ui recipe, with a limited subset of items

Pam approved this in Slack.

Merged into 2.x.

Posthumous review:

Fine with this change, but the menu id change might need to be covered in a change record/release notes (as it's 2.x only I think is fine) if people might be using it in recipes extending Drupal CMS?

Right you are, that's a great point.

Wrote the CR.