Allow RSSI Level thresholds to be customized

RSSI Level thresholds can now be customized using an
overlay. Migrated calls of
WifiManager.calculateSignalLevel(rssi, numLevels) in
Wifi Service to WifiManager.calculateSignalLevel(rssi)
to take into account the overlaid thresholds.

Bug: 140781184
Test: atest FrameworksWifiTests
Test: overlay thresholds, see that
calculateSignalLevel(rssi) uses the overlaid thresholds.

Change-Id: Ib9d0a3da363d152d6c4f49c26431fede4c3acdab
7 files changed