VT: Introduce dynamic jitter buffer for RTP source

A jitter calculator decides how much time is proper jitter time.
This helps to have shorter buffering time as per network status.

The formula of the calculation is defined in 6.4.1 of RFC3550.

* Added unit postfix 'Ms' for all variables related to the jitter time.
** Unified all default jitter value to kStaticJitterTimeMs.
*** Now a RR includes interarrival jitter time information.

Bug: 183578712

Change-Id: I9c442a801029680fc6c5227a14c243f13c89e3fa
Signed-off-by: Kim Sungyeon <sy85.kim@samsung.com>