Supported minimum aggregated bandwidth and roaming for 5G+

1. Added minimum bandwidth support. 5G+ icon is only
   shown when the aggregated bandwidth is above the threshold.
2. Allowed carrier to disable 5G+ while roaming.

Bug: 198831438
Bug: 201455505
Test: atest NetworkTypeControllerTest
Change-Id: I1359fab6f43308e725674089e68b2cd02e5d7358