test/binding: inherit PhysicalGpu from Handle

And rename PhysicalGpu to PhysicalDevice, gpu to phy.
diff --git a/tests/image_tests.cpp b/tests/image_tests.cpp
index b7702dc..dd60907 100644
--- a/tests/image_tests.cpp
+++ b/tests/image_tests.cpp
@@ -225,7 +225,7 @@
     mem_info.allocationSize = mem_req.size;
     mem_info.memoryTypeIndex = 0;
 
-    err = m_device->gpu().set_memory_type(mem_req.memoryTypeBits, &mem_info, 0);
+    err = m_device->phy().set_memory_type(mem_req.memoryTypeBits, &mem_info, 0);
     ASSERT_VK_SUCCESS(err);
 
     /* allocate memory */