Add explicit fedora version to channel chooser widget

[castrojo]

It'd be nice if we could show the F40, F41, etc versions of Fedora for people who want to lock into a version instead of a rolling tag.

[dnikoloski]

Do we want this hard-coded like:
Choose:

  date (F40)
  latest (F40)
  gts (F39)
  stable (F40)

[castrojo]

Yeah but ideally we don't want to have to update each one manually every time if there's a release if possible.

See also: ublue-os/config#251

[Malix-Labs]

• I propose we make ujust rebase-helper display a selection menu with the whole table from https://docs.projectbluefin.io/administration#upgrades-and-throttle-settings
• I also propose to reorder the channels :

  1. Current (replace with current channel name and remove it from below)
  2. Default (currently GTS)
  3. Stable
  4. Latest
  5. Date