[Feat] (DirectVulkan): run the tessellation stages

The backend already turned a tessellation control/evaluation shader into the
right VkShaderStage, but nothing downstream knew what to do with it: GL_PATCHES
had no topology, so it fell through to the triangle-list default, and the
pipeline carried no tessellation state at all. A GL_PATCHES draw therefore ran
the vertex and fragment stages over raw triangles.

Map GL_PATCHES to VK_PRIMITIVE_TOPOLOGY_PATCH_LIST, carry GL_PATCH_VERTICES into
the pipeline as patchControlPoints (part of the key, since two patch sizes are
two pipelines), attach VkPipelineTessellationStateCreateInfo for a patch topology
only, and enable the tessellationShader device feature.

POST reports the feature, because without it a program with a tessellation stage
cannot build a pipeline at all and GL_PATCHES draws render nothing.

MobileGL/MG_Util/Converters/MGToVk/RenderStateEnumConverter.cpp

@@ -38,6 +38,10 @@ namespace MobileGL {
                 return VK_PRIMITIVE_TOPOLOGY_TRIANGLE_LIST_WITH_ADJACENCY;
             case GL_TRIANGLE_STRIP_ADJACENCY:
                 return VK_PRIMITIVE_TOPOLOGY_TRIANGLE_STRIP_WITH_ADJACENCY;
+            case GL_PATCHES:
+                // The tessellator decides what a patch becomes; its vertex count is pipeline
+                // state (patchControlPoints), not part of the topology.
+                return VK_PRIMITIVE_TOPOLOGY_PATCH_LIST;
             default:
                 MGLOG_W("Unrecognized primitive topology");
                 return VK_PRIMITIVE_TOPOLOGY_TRIANGLE_LIST;

MobileGL/MG_Util/SelfTest/DriverPost.cpp

@@ -1431,6 +1431,18 @@ namespace MobileGL::MG_Util::SelfTest {
                          "hard-fails at draw");
         }
 
+        // Core 1.0 features the backend turns GL stages into pipeline stages with.
+        VkPhysicalDeviceFeatures coreFeatures{};
+        vkGetPhysicalDeviceFeatures(physicalDevice, &coreFeatures);
+        if (coreFeatures.tessellationShader == VK_TRUE) {
+            builder.Pass("tessellationShader",
+                         "supported (GL_PATCHES draws run the tessellation control/evaluation stages)");
+        } else {
+            builder.Warn("tessellationShader",
+                         "unsupported; a program with a tessellation control/evaluation shader cannot build a "
+                         "pipeline, so GL_PATCHES draws render nothing");
+        }
+
         Bool vertexAttributeInstanceRateDivisor = false;
         if (vkGetPhysicalDeviceFeatures2Fn != nullptr &&
             HasVkExtension(deviceExtensions, VK_EXT_VERTEX_ATTRIBUTE_DIVISOR_EXTENSION_NAME)) {