libobs-winrt: Remove interop code now provided by Windows SDK

[MrMahgu]

Description

Remove the custom declarations of the external functions CreateDirect3D11DeviceFromDXGIDevice and CreateDirect3D11SurfaceFromDXGISurface, as well as the IDirect3DDxgiInterfaceAccess interface.

Add WinSDK interop header: windows.graphics.directx.direct3d11.interop.h

Motivation and Context

This cleanup simplifies our codebase and ensures we're utilizing the standard, up-to-date definitions provided by the Windows SDK.

How Has This Been Tested?

Tested AMD Windows 11 with WinSDK 10.0.22621.0. Header file exists in WinSDK 10.0.20348.0 as well, with same code definitions.

Types of changes

• Code cleanup (non-breaking change which makes code smaller or more readable)

Checklist:

• [x] My code has been run through clang-format.
• [x] I have read the contributing document.
• [x] My code is not on the master branch.
• [x] The code has been tested.
• [x] All commit messages are properly formatted and commits squashed where appropriate.
• [ ] I have included updates to all appropriate documentation.

[MrMahgu]

not really sure how/if I did that right, but feel free to close this pr. If wanted, someone will do it.