If data switched to grouped CBRS subscription, show its provider name.

For testing purpose, we want system UI to show grouped CBRS carrier name
as in the upper left corner in system UI.
This is only a temporary change, and should be reverted in b/130246708.

Bug: 129865342
Test: manual
Change-Id: Ic8123215bb4ce5b9d757ff2ca3cfff1525fa0867