binder: Notify iface add/remove to binder

Notify |BinderManager| about any new iface addition/removal from
|wpa_supplicant| core.
|Iface| objects are stateless in the sense that they only
hold the name of the iface it controls. Every RPC call through the iface object
will first invoke |wpa_supplicant_get_iface| to ensure that the iface still
exists in the wpa_supplicant core.

While there,
1. Add some debug logs in binder.cpp.
2. Change C style comments to c++ style.
3. Add @utf8incpp annotation at the interface level in all the aidl files.

BUG: 29998764
TEST: Tested using the |gTest| integration tests. Will upload these under
|wificond|

Change-Id: If69bfaece7a6f69640fe8cbf90d1006a88aef8af
Signed-off-by: Roshan Pius <rpius@google.com>
8 files changed