Add ability to show a warning banner in User Dashboard

Once merged upstream, we'll need a respin of:

• dashboard - https://github.com/eclipse-che/che-dashboard/pull/478
• operator - https://github.com/eclipse-che/che-operator/pull/1339#issuecomment-1068150218
• metadata + bundle images

Note that we won't actually be SHOWING any thing new until we have an approved message w/ a link to a landing page that can be updated closer to DS 3.0 GA as needed.

I suggest the page should be at

https://developers.redhat.com/products/devspaces/overview

Message could be:

The next release uses a new DevWorkspace engine, and existing workspaces will need to be converted to the new format. >Click here to learn how to update and migrate.<