Add new config to tell us whether brightness is bucketed or continuous

If we know brightness is bucketed rather than continuous, then we skip
the brightness animation and just go straight to the expected brightness
level.

Bug: 64007419
Test: manual
Merged-In: I2ac0c5f45cc2ec1e758bb84a29d2ecda2c6d5b0d
Change-Id: I2ac0c5f45cc2ec1e758bb84a29d2ecda2c6d5b0d