Over a year ago, we completely re-vamped scrollbars while avoiding making any breaking changes.
Once they reached stable, the API was further iterated on as users started adopting the new scrollbar widgets.
There have been a lot of changes made, and I think we should now tidy up the API - especially with the ability to write dart fixes, it will be much easier to clean everything up nicely.

I thought I could do this in one go (#96935), but the change grew to be pretty large, so I am going to split it up and track it here.

Affected classes:

• RawScrollbar

• Scrollbar (_MaterialScrollbar)

• CupertinoScrollbar

• ScrollbarThemeData

• Add thumbVisibility across all

  • Deprecate Scrollbar isAlwaysShown -> thumbVisibility #96957

• Deprecate isAlwaysShown across all

  • Deprecate Scrollbar isAlwaysShown -> thumbVisibility #96957

• Add trackVisibility, trackColor, trackBorderColor to RawScrollbar

  • Update RawScrollbar to support the track #97335

• Deprecate showTrackOnHover in material library (widget & theme)

  • Deprecate Scrollbar hoverThickness and showTrackOnHover #97173

• Deprecate hoverThickness in material library (widget & theme)

  • Deprecate Scrollbar hoverThickness and showTrackOnHover #97173