This also allows WiFi passwords to be remembered. The underlying
tool (connman) allows to store passswords (that's why it auto connects
whenever you boot a Lakka device), so we expose this so that the user
does not have to re-input the pass when connecting to a saved wifi.
Option to forget a password to come in a future PR, for now a password
is automatically forgotten if the Wifi connect operation fails (we assume
it fails due to password).
Changes the WiFi API to enable these features of course!
This sets the ground for more PRs to come. Clean up how scanning and listing
SSID works, and adds attributes to the newtworks.
Frontend will be able to know which networks are "remembered" and thus
require no password to re-connect.
For now scans are performed every 2 minutes or on demand if no networks found
(either for real or in the "cache").
Adds an option to start wireless access point directly from RetroArch
settings menu (Services submenu). This wireless access point can be then
used for local netplay. If not defined in a specific config file
(LAKKA_LOCALAP_PATH), the arbitrary values for SSID/PassKey of the
created access point are LakkaAccessPoint/RetroArch. The menu/option is
added only in case when compiling with HAVE_LAKKA.
`connmanctl services` output is something like this:
```
Δ connmanctl services
NetMASTER Uydunet-N4832 wifi_742f68cd1f13_4e65744d415354455220557964756e65742d4e34383332_managed_psk
DIRECT-Dn-Android_d703 wifi_742f68cd1f13_4449524543542d446e2d416e64726f69645f64373033_managed_psk
PS4-8E777390BB63 wifi_742f68cd1f13_5053342d384537373733393042423633_managed_psk
```
So, instead of assuming the SSID length, just split the lines by space
character, and treat the last item as the unique id.
Updates libretro/Lakka#538
