Failed to update uniform buffer via Metal backend in ALL backend unittests

[bitmacs]

Hi, I've found that the lib backend unit tests with Metal-enabled failed when updating uniform buffers while switching to OpenGL is ok. Take TEST_F(BackendTest, BufferObjectUpdateWithOffset) for an example, the color is always black. In the meantime, samples such as hellotriangle works like a charm.

issue tags: v1.29.0, v1.42.0 OS: macOS 13.4.1