Expose Direct3D backend

[Kation]

Description of Change

Expose Direct3D backend

SkiaSharp Issue

Related to mono/SkiaSharp#2817

API Changes

Added:

• gr_direct_context_t* gr_direct_context_make_direct3d(const gr_d3d_backendcontext_t d3dBackendContext);
• gr_direct_context_t* gr_direct_context_make_direct3d_with_options(const gr_d3d_backendcontext_t d3dBackendContext, const gr_context_options_t* options);
• gr_backendtexture_t* gr_backendtexture_new_direct3d(int width, int height, const gr_d3d_textureinfo_t* d3dInfo);
• gr_backendrendertarget_t* gr_backendrendertarget_new_direct3d(int width, int height, const gr_d3d_textureinfo_t* d3dInfo);

Behavioral Changes

None.

Required SkiaSharp PR

None.

PR Checklist

• Rebased on top of skiasharp at time of PR
• Changes adhere to coding standard
• Updated documentation

[Kation]

@dotnet-policy-service agree

[mattleibow]

Thanks for this PR - I see CI is green. I have a whole bunch of comments that is more just API shape and general interop.