Add a Focus prefix to GitHub actions

[gabrielluong]

Similar to mozilla-mobile/firefox-android#47, we want to prefix github actions in Focus that are common between Fenix and Focus. We're adding a Focus prefix to the existing GitHub actions filenames and titles to help differentiate the actions. This will be needed when we migrate the remaining Fenix and Focus GitHub actions in the future where it would be otherwise hard to tell what the action is doing if they are named the same or it is unclear which subfolder the action is operating on.