[Feat] (MG_State/RenderState, MG_Backend/DirectVulkan): make Distant

Horizon work
- Implement BlendEquation/CullFaceMode/PointSize/PolygonMode
- Implement GetFramebufferAttachmentParameter*
- Downgrade some color attachment resolve failure
- Downgrade some overly-strict shader stage linkage check (don't check
  on unused input var)

MobileGL/MG_Util/Converters/MGToVk/RenderStateEnumConverter.cpp

@@ -103,5 +103,22 @@ namespace MobileGL {
                 return VK_BLEND_FACTOR_ONE;
             }
         }
+
+        VkBlendOp ConvertBlendEquationToVkEnum(BlendEquation v) {
+            switch (v) {
+            case BlendEquation::Add:
+                return VK_BLEND_OP_ADD;
+            case BlendEquation::Subtract:
+                return VK_BLEND_OP_SUBTRACT;
+            case BlendEquation::ReverseSubtract:
+                return VK_BLEND_OP_REVERSE_SUBTRACT;
+            case BlendEquation::Min:
+                return VK_BLEND_OP_MIN;
+            case BlendEquation::Max:
+                return VK_BLEND_OP_MAX;
+            default:
+                return VK_BLEND_OP_ADD;
+            }
+        }
     } // namespace MG_Util
 } // namespace MobileGL

MobileGL/MG_Util/Converters/MGToVk/RenderStateEnumConverter.h

@@ -16,5 +16,6 @@ namespace MobileGL {
         VkCullModeFlags ConvertCullFaceModeToVkEnum(CullFaceMode value, Bool invertClockwise = false);
         VkCompareOp ConvertDepthTestFuncToVkEnum(DepthTestFunc value);
         VkBlendFactor ConvertBlendFactorToVkEnum(BlendFactor value);
+        VkBlendOp ConvertBlendEquationToVkEnum(BlendEquation value);
     } // namespace MG_Util
 } // namespace MobileGL