1. QR code scanner (Wi-Fi Easy Connect) does not support sharing Wi-Fi hotspot
at current stage
2. Wi-Fi hotspot QR code button only shows when Wi-Fi hotspot is enabled
3. The QR code has the security string "WPA" for hotspot's WPA2_PSK
Bug: 123151660
Test: atest WifiTetherSSIDPreferenceControllerTest
WifiQrCodeTest WifiDppConfiguratorActivityTest
WifiDppEnrolleeActivityTest
WifiDppQrCodeGeneratorFragmentTest
WifiDppQrCodeScannerFragmentTest
WifiNetworkListFragmentTest
WifiDppChooseSavedWifiNetworkFragmentTest
Change-Id: I2e89450180b82cc841ee3b15be52bfc6f9f6164d