GStreamer: Add qml6d3d11 Video Sink

[HTRamsey]

Uses D3D11 instead of OpenGL on Windows

[Copilot]

Pull Request Overview

This PR adds a Direct3D11-based video sink path for Windows by introducing new D3D11 sink components, updating build configurations, and selecting the appropriate sink and graphics API at runtime on Windows.

• Introduce gstqgcvideosinkbin_d3d11 and qml6d3d11sink for Windows, alongside registration and plugin support.
• Update CMake and FindGStreamer.cmake to include and link the D3D11 GStreamer component.
• Adjust runtime selection in GStreamer.cc, GstVideoReceiver.cc, QML registrations, and application initialization to use D3D11 on Windows.

Reviewed Changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
gstqml6gl/CMakeLists.txt	Force shader resource cache override
gstqgc/gstqgcvideosinkbin_d3d11.h/.cc	Added D3D11 sink bin type and implementation
gstqgc/gstqgcvideosinkbin.h/.cc	Renamed QML GL sink fields to match qml6glsink
gstqgc/gstqgcelements.h	Declared qgcvideosinkbind3d11 element
gstqgc/CMakeLists.txt	Include D3D11 source files on Windows
GstVideoReceiver.cc	Conditionally omit sync property on Windows
GStreamer.cc	Register and verify qml6d3d11 plugin; select sink by OS
CMakeLists.txt (GStreamer)	Add D3d11 to FindGStreamer components
cmake/find-modules/FindGStreamer.cmake	Support GStreamer D3d11 component and link libraries
.github/workflows/windows.yml & custom.yml	Bump Windows CI GStreamer version to 1.26.3
VideoManager.cc & QGCApplication.cc	Register new QML type and switch to Direct3D11 graphics API

Comments suppressed due to low confidence (3)

src/VideoManager/VideoReceiver/GStreamer/GstVideoReceiver.cc:1014

• The conditional around the "sync" argument leaves a dangling comma or removes it incorrectly on Windows. Refactor to add the sync property only when needed without breaking the argument list.

                 #ifndef Q_OS_WIN

src/VideoManager/VideoReceiver/GStreamer/GStreamer.cc:134

• Missing semicolon after GST_PLUGIN_STATIC_REGISTER(qml6d3d11), which will cause a compile error.

    GST_PLUGIN_STATIC_REGISTER(qml6d3d11)

src/VideoManager/VideoReceiver/GStreamer/GStreamer.cc:259

• Array size is declared as 2 but conditionally includes a third element (qml6d3d11) on Windows, leading to out-of-bounds initialization. Increase the size or use a dynamic container.

    static constexpr const char *pluginNames[2] = {