libobs-winrt: Capture secondary windows

[prgmitchell]

Description

Enable IncludeSecondaryWindows when available so child windows are captured on Windows 11 24H2 and later. Microsoft docs were my friend on this one but I really just copied what was being done in the same file for IsCursorCaptureEnabled.

Motivation and Context

Saw someone complaining in support that menus in Pro Tools weren't being captured with a window capture source.

How Has This Been Tested?

Tested v32.2.2 capturing Blender with WGC capture selected, the preferences menu was not visible in the capture. After these changes the preferences window was now captured. I don't have an older build of Windows to test on but behavior should be unchanged there since we are checking for IncludeSecondaryWindows at runtime before this is enabled.

Types of changes

• Tweak (non-breaking change to improve existing functionality)

Checklist:

• I have read the contributing document.
• My code has been run through clang-format.
• My code follows the project's style guidelines
• My code is not on the master branch.
• My code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.