[SB Refactor] Define MobileNetworkTypeIcon as an eventual replacement of

MobileIconGroup and define a converter to convert from old to new.

Also updates MobileIconGroup to just automatically fill in all the
fields that are the same for all mobile icons.

Bug: 238425913
Test: atest SystemUITests
Test: MobileNetworkTypeIconsTest
Change-Id: Ie4faca5a1001bf0c3b3d4854b3469b956fa47370