Refactor vc_mgr_ducking module implementation

Refactor vc_mgr_ducking module implementation

This patch includes these features:
- Use predefined macro instead of magic number
- Use error enum value instead of magic number
- Enhance log content for debugging and changed function name.
- Use cpp for implementing vc_mgr_ducking module for future
enahancement.
- Create unit functions in vc_mgr_ducking module for higher
maintainability.
- Add sound stream type for ducking TTS sound volume.

Change-Id: I0d7d7d4bbe7d8aaa89546f127eba8a853b9e45d2
Signed-off-by: Suyeon Hwang <stom.hwang@samsung.com>