Improve/fix picking

Created by: RandomShaper

• Acknowledge mouse button events as position tellers (to make picking more solid; for instance, the touch mouse is raised with a mouse unpressed event that may have a more current position)
• Forget mouse position for physics if touch mouse raised (because the position known as last is no longer meaningful)
• Remove needless check for mouse over/exit (now there's code to inject an spurious move to ensure repicking if camera/objects have moved) <- @reduz, please confirm my assumption here is valid
• Restrict 2D mouse over/exit to mouse events (including emulated from touch; true touches shouldn't trigger the signals; they are just sent as events)
• Assign a device id of -1 to emulated mouse events

Fixes #26460 (closed).