feat(controls): Add TimePicker control

[OneEyedOlaf]

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?

The library currently lacks a dedicated TimePicker control.

What is done?

1. Basic control structure and logic.
2. A functional UI that works correctly in the light theme.

What is the new behavior?

This PR introduces a new TimePicker control.

Other information

As I am new to WPF and not yet fully familiar with the wpf-ui styling and brush system, I have only implemented the basic functionality and a simple UI for the light theme.

[chucker]

I know this is only the gallery page, but: typo

[chucker]

Thanks for your contribution; this is a great start. A few things I've noticed:

• the popup doesn't properly obscure the background. Notice how I can read the word "Source code":

• when no value has been picked, WPF UI Gallery used to show placeholder text, which I no longer see with this PR. That also matches how WinUI 3 Gallery shows the control.

• the list boxes should be taller. WinUI shows 9 items; this PR shows 3.
• scroll arrow-like buttons should be added. Here's how WinUI shows those (on hover of the respective column):

• to make the popup less jarring, the control's sections should align with it (i.e., space the two to three sections out), and the popup itself should vertically align with the control), the way WinUI does it:

• WPF UI doesn't yet support the "subtle" style, so we can't use that, but maybe the buttons should use icons instead of labels: