Allow tapped events with mouse movement to reach underlying widgets in Scroll

[dweymouth]

Description:

Remove Draggable interface from internal/widget/scroll to ensure that it won't unnecessarily swallow tap events if the mouse moves during the tap. Scrolling for mobile has been handled by the driver directly for awhile so the Draggable interface for mobile was redundant.

Fixes #4384

Checklist:

• Tests included.
• Lint and formatter run with no errors.
• Tests all pass.

Where applicable:

• Public APIs match existing style and have Since: line.
• Any breaking changes have a deprecation path or have been discussed.
• Check for binary size increases when importing new modules.