stream-manager: Support ducking API

stream-manager: Support ducking API

- Add new handler for ducking API

  server          : org.pulseaudio.Server
  object path     : /org/pulseaudio/StreamManager
  interface       : org.pulseaudio.StreamManager

  method name     : ActivateDucking
  method argument : unsigned int for stream index
                    boolean for enable
                    string for target stream
                    unsigned int for duration
                    double for ratio
  return value    : string for return message
                    - success : "STREAM_MANAGER_RETURN_OK"

[Version] 11.1.58
[Issue Type] New feature

Change-Id: Ib10aa11fe84ff73419798ead2b0db3b3f88c3c74
Signed-off-by: Jeongmo Yang <jm80.yang@samsung.com>