[SB Refactor] Display carrier merged wifi networks as mobile.

This CL:
1) Makes WifiRepository an input to MobileConnectionsRepository so that
   the mobile repo will know when there's a carrier merged connection.
2) Creates CarrierMergedConnectionRepository, which fills in the correct
   mobile values based on the carried merged wifi connection.
3) Creates FullMobileConnectionRepository, which switches between a
   typical mobile repo and a carrier merged repo based on the wifi
   network status.

Bug: 238425913
Bug: 264684296
Test: `adb shell am broadcast -a com.android.systemui.demo -e command
network -e wifi carriermerged -e level 2` -> displays a mobile triangle
with level 2 and "W+" as its RAT type (note: this will only work if the
next CL is also patched in)
Test: See additional test steps in second bug
Test: atest CarrierMergedConnectionRepositoryTest
Test: atest MobileConnectionsRepositoryTest
Test: atest FullMobileConnectionRepositoryTest
Test: all tests in statusbar.pipeline

Change-Id: I649b91984bf249d783e3117b30820289d78d82af