[Provider Model] Reduce the max of WiFi networks (QS Internet Dialog)

- The max of 3 wifi networks when Wi-Fi is on (regardless of if airplane
mode is on or off).

- The max of 6 items in Internet Panel.

- See b/206807144#comment20 for a video.

Bug: 206807144
Test: manual test
atest -c InternetAdapterTest \
         InternetDialogControllerTest \
         InternetDialogTest

Change-Id: Ia7889a78a6d803fbb5c5ac9107dcc4033626a27b