Scan parameter optimization

1) Adjust balanced/low power scan parameter based on the lab results.
2) Make screen off mode parameters configurable.
3) Reduce low latency mode scan interval to 100ms for the better channel
   diversity. Test results indicate there is no change of discovery
   latency with the small scan interval in the home environment.

Bug: 214595841
Test: manual with BLE scan app to ensure scan parameters are set
correctly.

Change-Id: I71f27621b5fe6e36203d8b78d44b9e21f0fa7ec5