[Dev 2.0] Added DropDownList, ComboBox and improved ScrollViewer

[veler]

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• New feature or enhancement
• UI change (please include screenshot!)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Internationalization and localization
• Other (please describe):

What is the current behavior?

1. DevToys 2.0 was missing a DropDownList.
2. DevToys 2.0 was missing a ComboBox.
3. I was unhappy with ScrollViewer we had so far. An issue in WebView2 in WPF (issue doesn't repro in WASDK or Safari (MAUI on Mac)) cause the scrollbar's width change on mouse hover to shift the content of the scrollviewer. See video below:

Recording.2023-06-10.215230.mp4

What is the new behavior?

• Added a DropDownList
• Added a ComboBox
• Adopted SimpleBar library for the scrollbar. This library replies on the native scrollbars of the web browser but replace their design. This is different than JavaScript libraries that "emulate" the scrollbar. Here, we keep the smoothness of the native scrollbars of the web browser.

Other information

Recording.2023-06-10.215634.mp4

Quality check

Here is a known issue. Will be addressed later

Before creating this PR:

• Did you follow the code style guideline as described in CONTRIBUTING.md
• Did you build the app and test your changes?
• Did you check for accessibility? On Windows, you can use Accessibility Insights for this.
• Did you verify that the change work in Release build configuration
• Did you verify that all unit tests pass
• If necessary and if possible, did you verify your changes on:
  • Windows
  • macOS (DevToys 2.0)
  • Linux (DevToys 2.0)