Common keys for video QP manipulation

Definitions for managing Video encoding Quantization Parameter (QP).
Providing a standardized key instead of various vendor-specific keys.

Bug: 161486623
Test: build, b/179554934 for functionality
Change-Id: I8f1976cff55e119a2b42332de3d7ae690dc9e1fa
(cherry picked from commit de66953c)