Using gnome-3-34 gives us a newer stack in general
and also provides us with a sdk build-snap, so we don't need
to specify as many build-packages and stage-packages.
This makes the snap slimmer and delegates the responsibility
for security updates to the gnome platform snap for even more
packages.
As per https://snapcraft.io/docs/snap-layouts,
bind-mounts significantly increase the startup time of the snap.
Use symlink instead for better performance.
Remove all files from snap that are already included in the base snap
or in any connected content snaps.
The main advantage is the massively reduced snap size:
From ~70 MB down to ~6 MB.