Implement FadingMaterial frag/vert shaders on core profile

Summary:
Like all the inbuilt shaders this now has a separate GLS source file which
works with a newer version without requiring compatibility.

Was https://git.reviewboard.kde.org/r/128426/

Test Plan:
Ran plasmashell with ForceGlCoreProfile set in the config
Hovered an icon in the task manager and it animated to the correct one
correctly.
Ran glslangValidator on both files. No warnings.

Reviewers: #plasma, mart

Reviewed By: mart

Subscribers: mart, plasma-devel, #frameworks

Tags: #plasma, #frameworks

Differential Revision: https://phabricator.kde.org/D4851

src/declarativeimports/core/fadingmaterial_core.frag

@@ -0,0 +1,11 @@
+#version 150 core
+in highp vec2 v_coord;
+uniform sampler2D u_src;
+uniform sampler2D u_target;
+uniform highp float u_transitionProgress;
+uniform lowp float qt_Opacity;
+void main() {
+    lowp vec4 tex1 = texture2D(u_target, v_coord);
+    lowp vec4 tex2 = texture2D(u_src, v_coord);
+    gl_FragColor = mix(tex2, tex1, u_transitionProgress) * qt_Opacity;
+}

src/declarativeimports/core/fadingmaterial_core.vert

@@ -0,0 +1,9 @@
+#version 150 core
+uniform highp mat4 qt_Matrix;
+in highp vec4 qt_Vertex;
+in highp vec2 qt_MultiTexCoord0;
+out highp vec2 v_coord;
+void main() {
+    v_coord = qt_MultiTexCoord0;
+    gl_Position = qt_Matrix * qt_Vertex;
+}

src/declarativeimports/core/shaders.qrc

@@ -2,5 +2,7 @@
 <qresource prefix="/plasma-framework/shaders">
     <file>fadingmaterial.vert</file>
     <file>fadingmaterial.frag</file>
+    <file>fadingmaterial_core.vert</file>
+    <file>fadingmaterial_core.frag</file>
 </qresource>
 </RCC>