Camera: Lazy load sound files to speed up camera startup

Lazy loading of sound files can speed up camera startup more than 60ms,
it gives users a great experience. Many apps do not playSound when camera
open or they may use their own audio files. so we load audio files as needed.

Bug: 128432959
Test: install wechat app,open camera,use systrace to see the uiThread wait time.
Change-Id: I3b3697cf9d0d919b88276f6d8e7fdd84578f4fcd