platform: Group `nm_platform_wifi_get_{bssid,rate,quality}` in one call: `nm_platform_wifi_get_station`

As proposed in !652 (closed) comments, try to make the platform wifi API better map to the NL80211 driver so that we don't have to use the workarounds added in that merge request for avoiding having each of the individual getters generate a new big NL80211 dump.