Terrain/sphrose/surface gradient list component (#4409)

* cherry-pick conflict fix

Signed-off-by: sphrose <82213493+sphrose@users.noreply.github.com>

* Missed include file

Signed-off-by: sphrose <82213493+sphrose@users.noreply.github.com>

* review changes.

Signed-off-by: sphrose <82213493+sphrose@users.noreply.github.com>

* cherry-pick merge fix

Signed-off-by: sphrose <82213493+sphrose@users.noreply.github.com>

* review changes.

Signed-off-by: sphrose <82213493+sphrose@users.noreply.github.com>

* bug fix

Signed-off-by: sphrose <82213493+sphrose@users.noreply.github.com>

* review changes.

Signed-off-by: sphrose <82213493+sphrose@users.noreply.github.com>

* compile fix

Signed-off-by: sphrose <82213493+sphrose@users.noreply.github.com>

* compile fix

Signed-off-by: sphrose <82213493+sphrose@users.noreply.github.com>

Gems/Terrain/Code/Source/EditorTerrainModule.cpp

@@ -9,6 +9,7 @@
 #include <EditorTerrainModule.h>
 #include <EditorComponents/EditorTerrainHeightGradientListComponent.h>
 #include <EditorComponents/EditorTerrainLayerSpawnerComponent.h>
+#include <EditorComponents/EditorTerrainSurfaceGradientListComponent.h>
 #include <EditorComponents/EditorTerrainSystemComponent.h>
 #include <EditorComponents/EditorTerrainWorldComponent.h>
 #include <EditorComponents/EditorTerrainWorldDebuggerComponent.h>
@@ -23,6 +24,7 @@ namespace Terrain
             {
                 Terrain::EditorTerrainHeightGradientListComponent::CreateDescriptor(),
                 Terrain::EditorTerrainLayerSpawnerComponent::CreateDescriptor(),
+                Terrain::EditorTerrainSurfaceGradientListComponent::CreateDescriptor(),
                 Terrain::EditorTerrainSystemComponent::CreateDescriptor(),
                 Terrain::EditorTerrainWorldComponent::CreateDescriptor(),
                 Terrain::EditorTerrainWorldDebuggerComponent::CreateDescriptor(),