Install topIcons GNOME Shell extensions, v25.

https://extensions.gnome.org/extension/495/topicons/
Installed from http://94.247.144.115/~git/topicons.git

This will allow us to workaround the fact that a few of the applets we use
hijack the notification area, and are therefore basically unusable in
GNOME Shell.
Enable the topIcons GNOME Shell extension.
Disable Florence's floating icon.

Its applet is now visible, "thanks" to the topIcons extension.
Revert "Stack another workaround on #8271."

This reverts commit 906940a18fbd698d218426cb38d394575d0217e9.
Revert "Add test suite workaround for #8010."

This reverts commit 992cc82e82fc892bb9809b7d1f5ed968d87e0abe.