Hotspot: add config to save passpoint on/off state

Add a new state in Settings provider to save whether hotspot 2.0,
i.e, passpoint, is enabled or not. In Settings, the user can manually
enable or disable this feature from UI. This enhanced feature is
controlled by flex config_passpoint_setting_on.

CRs-Fixed: 1039253
Change-Id: I0e8ce4d3da10532bf3aa736b0bbb24faa4655551