Determine dragSpeed and shiftDragSpeed for draggable objects

[arouinfar]

@pixelzoom wrote in #54 (comment)

For tuning drag speeds, I added query parameter dragVelocity (default 500) and shiftVelocity (default 250). Since they affect all draggable objects, they should be used to tune one object at a time.

The query parameters have since been updated to dragSpeed and shiftDragSpeed. KeyboardDragListener currently supports two drag speeds, but a third speed has been proposed in phetsims/scenery#1601.

For now, I will focus on just the two supported speeds, and we can reassess if/when the third speed is added to KeyboardDragListener. I will also consider using different speeds for the measurement tools (compass and field meter) and the experimental equipment (magnets, coils).

[pixelzoom]

@arouinfar here's a table that you can fill in:

Component	dragSpeed	shiftDragSpeed
Bar Magnet	600	150
Electromagnet	600	150
Pickup Coil	600	150
Compass	150	50
Field Meter	150	50

[arouinfar]

Thanks for the table @pixelzoom, I've filled it out.

I chose slower speeds overall for the Compass and Field Meter. The rationale is that I want the dragSpeed to be slow enough to still be readable but not inconveniently slow. Additionally, the smaller the shiftDragSpeed, the more precisely the tools can be placed, which seems important.

We may need to refine these values as sound is integrated, but I tested these speeds with #77 and it sounded reasonable to me.

[pixelzoom]

Thanks @arouinfar. These values feel good to me, implemented in e855aa5. It was also necessary to delete ?dragSpeed and ?shiftDragSpeed. Back to you for a look, feel free to close.

[arouinfar]

Looks good on main, thanks @pixelzoom!