flatpak: Fix the tracker and tracker-miner builds

Intltool was removed from version 3.34 of the GNOME SDK, but it's still used by tracker-miners. Therefore it has to be bundled with the build.

Tracker's master branches are now being used to develop version 3.0, and it's not ready for use [1]. Hence the build has to be switched to use the respective 2.3 branches.

Some changes by Debarshi Ray.

[1] https://discourse.gnome.org/t/tracker-has-branched-for-3-0-use-the-2-3-branch-if-you-want-stability/1889

!118 (closed) !125 (merged)