Fixes some problems introduced by #49917
* Tree used minimum size as a stretch ratio, so it forced a minimum size of 1.
* Minimum size redone, stretch ratio moved to a separate setting
* Fitting to contents was enforced, this is more intuitive, but in many situations this is undesired.
* Added a clip content option for situations where fit to contents does not apply.
* Icon would scroll with the item, making it invislbe if the item is too long.
* Made icon always appear to the right (or left if RTL is enabled) of the visible item space.
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