Proposal: Add dark mode for window caption button tooltip

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

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