previously the game would go into an infinite loop at
https://github.com/wesnoth/wesnoth/blob/1.14.4/src/gui/widgets/window.cpp#L1046
when a tooltip doesn't fit on screen, this could in particular happen in
the mp lobby when hovering over the 'i' of a game that uses a ridiculous
amount of modifications.
I currently don't see any case where the game is actually able to 'fix'
a bad height that was reported from reevaluate_best_size. so i just
disable reevaluate_best_size for floating tooltips.
If there exists such a case, an alternative fix could be to change the
reevaluate loop in window::layout to also stop when a new iteration
returned the same size as the previous iteration.
(cherry-picked from commit 936516c83b6e0a6e76938c65158d2d6d98f94fba)
