Added NOT_METERED to mutable capabilities

NOT_METERED is the capability tied to APN type. Since
some APNs can be unmetered on IWLAN, this capability
can be dynamically changed. Should evaluate if using
TEMP_NOT_METERED in this case in the future.

Fix: 228996683
Test: atest DataNetworkTest
Change-Id: Icf8e5744ffaa7b330d9b7c7332b80abd8bde91a6