Context menus should pop beside the mouse cursor, not under it

System context menus on mac/Windows/Linux pop beside the mouse cursor, not beneath it. The new context menus can pop under the cursor if there is no room to the right of the cursor to open it. This covers the "context" of the item for which the menu refers.

Repro:

1. Move editor to the right hand side of the screen so there is not enough room to the right to pop the context menu to the right of the mouse cursor
2. Right click in the hierarchy view to open the mouse cursor

Result: Context menu pops under the mouse cursor

Expected: Context menu should pop to the left the cursor if there is not room to the right.

Repro environments: Mac / Windows / Linux