Rework `ComboBox`

[bdlukaa]

Is your feature request related to a problem? Please describe.
The current implementation of the ComboBox doesn't look good. Initially, it was built as a copy of the Material counterpart.

Describe the solution you'd like
I'd like to see the ComboBox reworked to use the fluent_ui built-in Flyout implementation, or potentially even OverlayPortal. This would bring its appearance and behavior much closer to the actual Windows Fluent design guidelines.

Describe alternatives you've considered
The main alternative is keeping the current Material-based implementation, but that defeats the purpose of having a dedicated Fluent UI library.

Additional context
Reworking this component will significantly improve the overall fidelity and feel of the library for users relying on dropdown/combo box inputs.

[WinXaito]

By the way, if you rework the ComboBox, the animation is hardcoded and should depend on the theme