Move hasSignificantWhitespace and handlesOwnChildren abstracts to ve.Node.

Change-Id: I10ffa5097d7df60a37ab7725422d64c6d99f3e34
Don't always use updateDimensionsDebounced

If the menu is shown but only moved after debounce, then it
visibly jumps from it's old position.

Bug: 73242
Change-Id: I7db94ec54cc2613a1a0cb3e86cf3a3724030901e
Don't allow dropping inside a handlesOwnChildren node

Bug: 73368
Change-Id: I56f1f84adb8602d3bf78bbe2ca3a6ace41438e54
Merge "Don't always use updateDimensionsDebounced"
Merge "Move hasSignificantWhitespace and handlesOwnChildren abstracts to ve.Node."
Merge "Don't allow dropping inside a handlesOwnChildren node"