Proposal: Add dark mode for window caption button tooltip

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### Title

Add dark mode support for window caption button tooltip

### Summary

When `ExtendsContentIntoTitleBar`, the window caption buttons are already self-drawn (as opposed to the standard win32 standard window caption buttons). It would be more consistent to support dark theme for the caption button's tooltip when the window content is also in dark mode.

### Rationale

Some software already does this (even Microsoft's own Visual Studio does this). This makes the window looks consistent and more polished.

|WinUI3 currently|Visual Studio Code|
|---|---|
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**But! Please fix #10438 first**

### Scope

| Capability | Priority |
| :---------- | :------- |
| The caption button tooltip automatically changes theme according to `Window.Content` | Must |
| Provide a API to set the caption button tooltip's theme | Could |
| Allow customizing the caption button tooltip with xaml (exactly like what Window Terminal already does) | Could |
| Fix existing incorrect tooltip as in #10438 | Must |

### Important Notes

_No response_

### Open Questions

_No response_

Start by reviewing issue #10438 and the existing caption button tooltip behavior in the WinUI repository. Compare the required automatic theme change with the optional API and XAML customization proposals, then verify that the tooltip follows Window.Content's theme and that the incorrect behavior described in #10438 is fixed.

Written by the indexing model from the issue text.