Add default implementation for dynamic volume config feature

- new dumpsys cmd "--audioPortChangeCallback" to trigger AudioPort
  callback. For now, limited to AudioGain stage updates only.
- AudioPort callback will carry the new gain stages information to
  the framework.

Bug: 261647905
Test: VTS

Change-Id: I404bde3671bf1ad39d1cb091ebf63d1049edec34
Signed-off-by: Raj Goparaju <rajgoparaju@google.com>