Move the nested struct inside VkNativeBufferANDROID outside.

The nested struct of VkNativeBufferANDROID in vk_android_native_buffer.h
needs to be moved outside to properly update the vulkan registry as
there is no way of specifying nested structs in the registry yet.

Bug: 136570819
Test: Build and flash, dEQP tests
Change-Id: I8b0db3f0729215f29ba82b6352010c7dd7f47f4e