Once a device has been scheduled for update mark the others from the same plugin
as updatable-hidden rather than updatable so that fwupdmgr or gnome-software
does not try to offer updates for them.
This is preferable to quitting with an error in FuDevice->prepare as we don't
want to waste bandwidth downloading the next update and then show the user an
error they can't possibly understand.
Exclude the currently scheduled device to allow the user to change the scheduled
release and so the pending device does not disappear from UI tools.
The end year is legally and functionally redundant, and more importantly causes
cherry-pick conflicts when trying to maintain old branches. Use git for history.
That giant uint64_t isn't looking so big now, and we'll want to add even more
to it in the future. Split out some private flags that are never useful to the
client, although the #defines will have to remain until we break API again.
