Fix cockpit console AppStream data
* Add missing header
* Update <extends> to renamed cockpit ID, as "cockpit.desktop" is
invalid (§ 2.1.3 [1]) and got changed in [2]
* Avoid dashes in <id> (§2.1.3) and use the actual project's home page.
Rename the file accordingly.
* Use a more verbose description from the home page ("style-invalid"
validation error)
* Avoid whitespace in <summary>
* Add homepage URL
* Add <update_contact>
`appstream-util validate src/cockpit/389-console/org.cockpit-project.389-console.metainfo.xml`
is happy now.
[1] https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#sect-Metadata-GenericComponent
[2] https://github.com/cockpit-project/cockpit/pull/11557
(cherry picked from commit 3347d922272c0be98978b3660fdf79f6930a0ec8)