Use DeviceConfig to get the default VelocityTracker strategy

To help with the rollout of the 'impulse' velocitytracker strategy, use the param 'velocitytracker_strategy' that was added in cr/428591953 in the VelocityTracker.java
This can be turned on using:
adb shell device_config put input_native_boot velocitytracker_strategy impulse
To check the current value:
adb shell device_config get input_native_boot velocitytracker_strategy

Bug: 134179997
Test: adb shell dumpsys input

Change-Id: I60fe3dd67983bb2c9e523f58b002cf58aeb9d793