windows-bindgen remove variant overrides

[Kenny Kerr (kennykerr)]

These are no longer required.

[Copilot]

Pull request overview

Removes previously hard-coded bindgen overrides by switching D2D_VECTOR_3F to the existing Numerics remap path and deleting now-redundant VARIANT/PROPVARIANT special-casing in bindgen’s struct codegen. This aligns Win32 projection output with the established Windows.Foundation.Numerics substitutions used throughout the windows crate.

Changes:

• Remove the locally-defined D2D_VECTOR_3F Win32 struct from the windows crate projection output.
• Add a bindgen remap from D2D_VECTOR_3F -> Windows.Foundation.Numerics.Vector3 (matching existing Vector2/Vector4 behavior).
• Delete unused VARIANT/PROPVARIANT overrides and constants in bindgen codegen.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
crates/libs/windows/src/Windows/Win32/dcommon/mod.rs	Drops the D2D_VECTOR_3F struct definition from the Win32 projection output.
crates/libs/bindgen/src/types/mod.rs	Adds D2D_VECTOR_3F -> Windows.Foundation.Numerics.Vector3 remap alongside existing Numerics substitutions.
crates/libs/bindgen/src/types/cpp_struct.rs	Removes VARIANT/PROPVARIANT special-case logic in clone/copyability decisions.
crates/libs/bindgen/src/type_name.rs	Removes now-unused TypeName::VARIANT and TypeName::PROPVARIANT constants.