GPU (macOS): use recommendedMaxWorkingSetSize as total GPU mem size

Worth noting that the value is static. It won't change even if the free global memory is smaller than the value.

src/detection/gpu/gpu_apple.m

@@ -68,6 +68,9 @@ const char* ffGpuDetectMetal(FFlist* gpus)
             gpu->type = device.location == MTLDeviceLocationBuiltIn ? FF_GPU_TYPE_INTEGRATED : FF_GPU_TYPE_DISCRETE;
             gpu->index = (uint32_t) device.locationNumber;
             #endif
+
+            if (device.hasUnifiedMemory && device.recommendedMaxWorkingSetSize > 0)
+                gpu->shared.total = device.recommendedMaxWorkingSetSize;
         }
         return NULL;
     }