Move all download.jboss.org content to a new host (including Che/CRW *.vsix files)

According to email thread and related to JBIDE-28286, we'll soon have to stop using download.jboss.org due to [404, reason not found].

Sounds like shutdown is planned for 31st Mar 2022, or before the release of Dev Spaces 3 (previously called CRW 2.16).

Existing refs to download.jboss.org include:

• https://github.com/redhat-developer/codeready-workspaces/blob/crw-2-rhel-8/dependencies/che-plugin-registry/che-theia-plugins.yaml#L19 (19 files)
• https://github.com/eclipse-che/che-plugin-registry/blob/main/che-theia-plugins.yaml (22 files)
• ... more?

Perhaps we can push content to GH releases, like we do for other CRW artifacts?

For upstream, I suppose we can publish content to GH releases as well.

TODO:

• update publishing process, including grabbing some old releases we still need (possibly manual steps?) (for both Che and CRW)
• update devfiles/plugins to point to new locations (for both Che and CRW)