Make Goto line a Popup and allow expressions

[kitbdev]

• originally a part of #86978

Changes Goto Line Dialog to be a popup, since it should be transient. Uses an EditorSpinSlider instead of just a LineEdit, so expressions are supported, as well as up/down arrow keys and dragging if you unfocus it with Tab. Pressing Enter closes the popup. The default popup position is at the top center of the TextEditor it is on.

Fixes Goto line not deselecting. Goto Line now centers to the line and sets the caret column to 0. Going to a method in the members overview now always sets it to the first line.