Add ability to revert slider settings to default when double-clicking nub

[Joehuu]

• Addresses Add "double click to reset to default value" for slider in menus #21505

Just a change I had hanging. Didn't do it in framework because it needs a nub to work (framework only implements the nub locally in a test).

[peppy]

Seems simple enough, works well.

If anything is going to fail with this, it's likely going to require changes to framework double-click handling (we don't use this in many places yet). Let's see.