[SB Refactor] Define WifiUiAdapter to interface between the new data

pipeline and the old UI.

When the new data pipeline detects a valid wifi icon, it will notify
StatusBarIconController to inflate a wifi icon if necessary.
This matches the pattern of MobileUiAdapter.

Bug: 238425913
Test: verify old wifi icon still works as expected
Test: verify new wifi icon still works as expected
Test: atest ModernStatusBarWifiViewTest StatusBarIconControllerTest
Change-Id: Id6a26bd00ee661a28e89585ea7b1293282a50c4d