[SB] Allow carrier merged connections to inflate their signal strength

Because carrier merged connections are rendered as mobile triangles,
they should be able to control the number of levels just like a typical
mobile connection.

Bug: 423686800
Flag: com.android.systemui.status_bar_inflate_carrier_merged
Test: atest CarrierMergedConnectionRepositoryTest

Test: With new flag on but Kairos off:
 (adb shell am broadcast -a com.android.systemui.demo -e command
network -e wifi carriermerged -e slot 2 -e level 4 -e numlevels 5 -e
inflate false) -> verify triangle with W+ displays with 4/4 bars filled
in (numlevels=5 means the level can be in range [0-4])
 (adb shell am broadcast -a com.android.systemui.demo -e command
network -e wifi carriermerged -e slot 2 -e level 4 -e numlevels 5 -e
inflate true) -> verify triangle with W+ displays with 5/5 bars filled
in

Test: With flag off: Verify those same test cases, but that they all
show 4/4 bars filled in

Change-Id: If250be73b3b86ac31237d4e11327c6233bc0221f