Add scrollbar style and behavior reactive update for Mac OS

[hamen]

Description

This PR adds MacScrollbarHelper. This file is heavily inspired by IntelliJ NSScrollerHelper. It has been converted to Kotlin, purged of what we don't need and migrated to Kotlin Coroutines.

MacScrollbarHelper API provides:

• scrollbarVisibilityStyleFlow: StateFlow<ScrollbarVisibility>
• trackClickBehaviorFlow: StateFlow<TrackClickBehavior>
• trackClickBehavior: TrackClickBehavior
• scrollbarVisibility: ScrollbarVisibility

The two flows have been plugged into the SwingBridgeService.currentBridgeThemeData: StateFlow<BridgeThemeData>. Every time the theme, the scrollbar visibility, or the track behavior change, we get an emission and whoever is listening gets an update.

The two properties replaced the original implementations we had in ScrollbarBridge.

Furthermore, this PR iterate once again on scrollbars colors on macOS.

Related Issues

#510 #445

Checklist

• I have executed the Pre-push Gradle task
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings

How Has This Been Tested?

• New and existing unit tests pass locally with my changes
• I have manually tested my changes on MacOS
  • With dark theme
  • With light theme
• I have manually tested my changes on Windows
• I have manually tested my changes on Linux

Screenshots or GIFs:

[rock3r]

Can you confirm this does not cause issues on Win/Linux? You specifically didn't check those boxes, and I'd like to be sure :)

[rock3r]

@hamen re:

Can you confirm this does not cause issues on Win/Linux? You specifically didn't check those boxes, and I'd like to be sure :)

Can you confirm it doesn't cause issues for Windows and Linux?