Improve progress calculation
Improve progress calculation

When calculating the progress of a flatpak installation,
it considers the extra-data and OSTree pull as different
operations and that makes the progress to go back and
forth between 0% and 100%.

Consumers of this API, like GNOME Software, end up having
a bad experience reporting the progress of a Flatpak app
instalation.

Fix that by using a set of heuristics to improve the process,
splitting the operation in parts that can be tracked (or at
least estimated).

GeorgesStavracas/flatpak,GeorgesStavracas/flatpak,matthiasclasen/flatpak,flatpak/flatpak,flatpak/flatpak,handsome-feng/flatpak,handsome-feng/flatpak,handsome-feng/flatpak,GeorgesStavracas/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,flatpak/flatpak,handsome-feng/flatpak,GeorgesStavracas/flatpak,handsome-feng/flatpak,GeorgesStavracas/flatpak,flatpak/flatpak