Tree view gets offset and stuck after scrolling and collapsing

[PriyanshC]

Example outcome (currently unable to scroll in this state):

Steps

1. Create a very wide tree (e.g. with an iterative parser)
2. Scroll far to the right side
3. Collapse the tree from a parent node to the iterative parser
   Result: Unable to scroll because the tree after collapsing isn't very wide, and can be difficult/impossible to re-expand it if its too far offset.
   This also affects the input (and presumably code) view.

Suggested fix - reset the scroll if the tree changes and the current horizontal position is above the new max scroll

[PriyanshC]

To be checked - may applies vertically too