Wifi: Allow configuration of Ad-Hoc (IBSS) networks

Show Ad-Hoc (IBSS) networks in the list of available Wi-Fi networks and allow
to connect to or create new Ad-Hoc (IBSS) networks.

This requires the IBSS changes in frameworks/base and external/wpa_supplicant_8

Change-Id: Ie44c47753100bbf8e691446e69b8d31659f64e3b
Wifi: Enable IBSS options only if IBSS is supported

Show IBSS network options only if IBSS mode is supported by the Wifi driver.

This makes use of the new API isIbssSupported() of WifiManager. We have to be
careful to make the query only after we reached WIFI_STATE_ENABLED.

WifiSettingsForSetupWizardXL is left out because it does not handle these
states.

Change-Id: I072c5cc6ed36305806b469cf05c4786d22bfd418
Wifi: Add frequency selection for new IBSS

Allow users to select a frequency for newly created Ad-Hoc (IBSS) networks, and
show the frequency for existing IBSS.

Change-Id: Icaa09c9386967fdf0a88865ff2e64cc9b219da1f