feat(controls): Fix Calendar styling

[Nuklon]

Pull request type

Please check the type of change your PR introduces:

• Update
• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes

What is the current behavior?

There are various problems with the current Calendar styling:

• No MouseOver background visible on date selection and various other buttons (e.g. the prev/next button and header).
• Focus style is very ugly.
• Doesn't match WinUI.
• Keyboard navigation doesn't work very well.

What is the new behavior?

Addresses all these points.

Old:

New:

Wpf.Ui.Gallery_6ze9MBPN0S.mp4

(also makes selecting current date have correct WinUI border).

WinUI 3:

Other information

There's one difference in that WinUI can focus Months/Year/Decades without moving the current selection. This isn't present in WPF so there are no separate focus styles for these.