Describe the problem

With the last changes in the color themes, we've accidentally broken the High Contrast theme, which now lacks some UI elements that are present in other themes and it results in a degraded experience.

Here is an example:

To reproduce

• open the Preferences
• enable the High Contrast (Theia) theme
• 🐛 UI is broken (missing hover status in dropdowns and in the sketchbook, primary buttons background is transparent, board selector has no border, etc...)

Expected behavior

• open the Preferences
• enable the High Contrast (Theia) theme
• 🦋 UI is not broken

Arduino IDE version

2.0.0-rc8-snapshot-4f27725

Operating system

macOS

Operating system version

MacOS Monterey 12.3.1

Additional context

No response

Issue checklist

• I searched for previous reports in the issue tracker
• I verified the problem still occurs when using the latest nightly build
• My report contains all necessary details