Added tooltip to sync collections FAB (bitfireAT/davx5#340)

* Added tooltip to sync collections fab

Signed-off-by: Arnau Mora <arnyminerz@proton.me>

* Greyscale tint for collections sync FAB

* Always use TooltipCompat for FAB tooltips

Closes bitfireAT/davx5#339

---------

Signed-off-by: Arnau Mora <arnyminerz@proton.me>
Co-authored-by: Sunik Kupfer <kupfer@bitfire.at>
Co-authored-by: Ricki Hirner <hirner@bitfire.at>