[Matrix] Implement matrix support for the `ddx` HLSL Function

> Note: This issue tracks matrix support for `ddx`. The original implementation issue is [here](https://github.com/llvm/llvm-project/issues/99096).

Matrix requirements:
- [ ] https://github.com/llvm/wg-hlsl/issues/387

## HLSL:

Returns the partial derivative of the specified value with respect to the screen-space x-coordinate.

| *ret* ddx(*x*) |
|----------------|

This function computes the partial derivative with respect to the screen-space x-coordinate. To compute the partial derivative with respect to the screen-space y-coordinate, use the [**ddy**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-ddy.md) function.

This function is only supported in pixel shaders.

## Parameters

| Item | Description |
|--------------------------------------------------------|----------------------------------------|
| *x*
| \[in\] The specified value.
|

## Return Value

The partial derivative of the *x* parameter.

## Type Description

| Name | [**Template Type**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-intrinsic-functions.md) | [**Component Type**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-intrinsic-functions.md) | Size |
|-------|----------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------|--------------------------------|
| *x* | [**scalar**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-intrinsic-functions.md), **vector**, or **matrix** | [**float**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src/WinProg/windows-data-types.md) | any |
| *ret* | same as input *x* | [**float**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src/WinProg/windows-data-types.md) | same dimension(s) as input *x* |

## Minimum Shader Model

This function is supported in the following shader models.

| Shader Model | Supported |
|-----------------------------------------------------------------------------|-------------------------------------------|
| [Shader Model 5](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/d3d11-graphics-reference-sm5.md) and higher shader models | yes |
| [Shader Model 4](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-sm4.md) | yes |
| [Shader Model 3 (DirectX HLSL)](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-sm3.md) | yes |
| [Shader Model 2 (DirectX HLSL)](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-sm2.md) | yes in ps\_2\_x; unsupported in ps\_2\_0. |
| [Shader Model 1 (DirectX HLSL)](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-sm1.md) | no |

This function is supported in the following types of shaders:

| Vertex | Hull | Domain | Geometry | Pixel | Compute |
|--------|------|--------|----------|-------|---------|
| | | | | x | |

## See also

[**Intrinsic Functions (DirectX HLSL)**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-intrinsic-functions.md)

Start by reading the original implementation issue #99096 and the matrix requirement in HLSL issue #387. Use the ddx specification in this issue to determine the expected matrix input and return behavior, including pixel-shader support. Done means matrix support is implemented and covered according to that requirement.

Written by the indexing model from the issue text.