wifi: Add support for SSID bridging

SSID bridging add support for below
- Enables roaming between different WPA/WPA2-PSK SSIDs with same default
  gateway MAC address
- Enables auto connection attempts to a new 5GHz SSID AP with current
  connected 2GHz SSID credentials

This commit adds below changes to enable SSID bridging
- Add global settings to enable/disable features
- Add "linkedNetworkId" parameter in WifiConfiguration. It is applicable only for
  new 5GHz SSID ephemeral configs. It is to link the ephemeral config with saved
  SSID 2GHz SSID config. SavedNetworkEvaluator gives current network bonus and
  last selected network bonus to the ephemeral config if "linkedNetworkId" is
  matches with current network ID.
- Add new system notification Id to notify new 5GHz SSID auto connection
  attempt result.

Change-Id: I12c131af556537ec8e83fea64fb69736845dbc6a
CRs-Fixed: 2585822