Don't register playback/recording change if caller doesn't care it

When calling VirtualDeviceManager#createVirtualAudioDevice(), if the
caller pass null AudioConfigurationChangeCallback parameter, it means
the caller doesn't care the audio playback/recording change in virtual
display, and we should not register it with AudioManager for
optimization.

Bug: 218528439
Test: atest CtsVirtualDevicesTestCases
Change-Id: I00120f2506f593100ef8c523a4f6addffe46597b