This is not used at the moment. It will be used in the following
commits to define the clip plane equations.

There is no need to define a special vertex shader code for this
material, it can use the default case. This way, it reduces the number
of vertex shader files.

This will be used by `QgsPhongMaterialSettings` in the next commit.

This commit makes two changes to `QgsPhongMaterialSettings`:
1. It merges `dataDefinedMaterial()` and `constantColorMaterial` into
one new function: `buildMaterial`.

2. The fragment shader files `phongDataDefined.frag` and
`phongConstant.frag` are merged into a new file `phong.frag`. This is
achieved by a `#define` logic. If `DATA_DEFINED` is defined, this is
the dataDefined case. Otherwise, this is the constant case.

This is similar to the previous QgsPhongMaterialSettings change:

This commit makes two changes to `QgsGoochMaterialSettings`:
1. It merges `dataDefinedMaterial()` and `constantColorMaterial` into
one new function: `buildMaterial`.

2. There is one fragment shader file called `gooch.frag`. This is
achieved by a `#define` logic. If `DATA_DEFINED` is defined, this is
the dataDefined case. Otherwise, this is the constant case.

There is no need to define a special vertex shader code for this
material, it can use the default case. This way, it reduces the number
of vertex shader files.

This is the same material as the qt3d one:
`Qt3DExtras::QTextureMaterial`. It will also be used in the following
commits to define the gl_ClipDistance for the textured terrain.

This is the same material as the qt3d one:
`Qt3DExtras::QgsMaskedTexturedMaterial`. It will also be used in the
following commits to define the gl_ClipDistance for the non texture
case of the terrain.

There is no functional change. It is simply needed to add
gl_ClipDistance support to the terrain shaders in the next commits.

`Qt3DRender::QClipPlane` enable OpenGL clipping plane that can be used
in shaders using gl_ClipDistance.

This change adds 4 clipPlane. This will be used to clip the 3dScene at
Xmin / Xmax / Ymin / Ymax. This change has no effect at the moment
because  `gl_ClipDistance` needs to be computed in each vertex or
geometry shader file. This will be achieved in the following commits.

This is achieved with two changes:
1. define the plane equation as uniform with the
`Qgs3DUtils::addBoundingBoxParametersToEffect` call
2. include `clipplane.inc` file in the vertex shader file and call
setClipDistance()

With these changes, the planes defined in the framegraph are used.

The associated unit test needs to be updated because the objects at
the border of the scene are now partially cut.

All the existing parameters are stored in
`Qgs3DMapSettings`. Therefore, `Qgs3DMapSettings` can be directly
used.

This is achieved with two changes:
1. define the plane equation as uniform with the
`Qgs3DUtils::addBoundingBoxParametersToEffect` call
2. include `clipplane.inc` file in the vertex shader file and call
setClipDistance()

With these changes, the planes defined in the framegraph are used.

This is achieved with two changes:
1. define the plane equation as uniform with the
`Qgs3DUtils::addBoundingBoxParametersToEffect` call
2. include `clipplane.inc` file in the vertex shader file and call
setClipDistance()

With these changes, the planes defined in the framegraph are used.

This is achieved with two changes:
1. define the plane equation as uniform with the
`Qgs3DUtils::addBoundingBoxParametersToEffect` call
2. include `clipplane.inc` file in the vertex shader file and call
setClipDistance()

With these changes, the planes defined in the framegraph are used.

This is achieved with two changes:
1. define the plane equation as uniform with the
`Qgs3DUtils::addBoundingBoxParametersToEffect` call
2. include `clipplane.inc` file in the vertex shader file and call
setClipDistance()

With these changes, the planes defined in the framegraph are used.

This one is a little bit to the other ones. Indeed, lines has a
geometry shader with redefine gl_Position. Therefore, gl_ClipDistance
needs to be computed in the geometry shader file.

With these changes, the planes defined in the framegraph are used.

This is achieved with two changes:
1. define the plane equation as uniform with the
`Qgs3DUtils::addBoundingBoxParametersToEffect` call
2. include `clipplane.inc` file in the vertex shader file and call
setClipDistance()

With these changes, the planes defined in the framegraph are used.

This is achieved with two changes:
1. define the plane equation as uniform with the
`Qgs3DUtils::addBoundingBoxParametersToEffect` call
2. include `clipplane.inc` file in the vertex shader file and call
setClipDistance()

With these changes, the planes defined in the framegraph are used.

This is achieved with two changes:
1. define the plane equation as uniform with the
`Qgs3DUtils::addBoundingBoxParametersToEffect` call
2. include `clipplane.inc` file in the vertex shader file and call
setClipDistance()

With these changes, the planes defined in the framegraph are used.