Ensure Visible off on wide cells

[davidkircos]

• When dragging to select large cells where the far right side is off screen, each cell you select moves the view port and it's impossible to select what you want.
• When reading a list of cells where the right edge is off screen, everytime you press down the viewport jumps to the bottom right of the selected cell, making it so you have to scroll back left on every cell.

We should really only be calling ensure visible when the cursor is fully off screen and when the user is using the keyboard.

If a user is selecting cells with the mouse, we should not move the viewport

(To successfully close this issue, the problems with users getting jumped around in the sheet should be fully solved. All navigating should work as expected; this bug is by far the biggest culprit but there might be other scenarios that are odd behavior)