Adding an option to install a certificate from the CA certificate menu

For CA ceritificate we only can install in Network Preferences > Advaned
> Install certificates. So we add the option for user to install when
you setup the wifi network. After you install the certificate, you can
see the certificate in your menu.

Bug: 176998563
Test: manual test
make RunSettingsRoboTests ROBOTEST_FILTER=WifiConfigController2Test

Change-Id: I532b12f9277c6a15c649907fa3711c807566c88e