While unfortunate that we still have to scan all apps with get_all(),
support for this feature will be short-lived, so hopefully we can drop
it in the future as new apps adapt to the desktop file / app ID
recommendations.
app-system: Lazily create ShellApps for apps we care about
Rather than create all ShellApps up-front, create them lazily. We really
had no reason to do this before as we were scanning GMenu to get all the
apps, but doing this can remove a need for get_all, which is slow and
memory-hungry.
appDisplay: Use a proper string key for the app search provider
We were always sort of cheating when we used objects as the search ID.
Since the new desktop file index will return us a list of desktop file
IDs, just use those as IDs instead.
We want to transition to a system in the future where we have a desktop
file cache. As we no longer differentiate categories or similar, it no
longer makes sense to have app visibility based on categories. Thus,
we no longer need to use gnome-menus to list all apps. The potential
issue here is reloading all desktop files when new files are created,
but this can be dealt with individually.
The "All Applications" view still uses gnome-menus.
Since appDisplay.js makes its own GMenu tree, it's not necessary
anymore. This does mean that searches will show apps in NoDisplay
categories, but that's an obscure enough edge case not to matter.
