Move Interface index name map dump to NetworkStatsService

Map status dump will do access check if map is null.
This could show different message from the current dump output.

Information in map content dump does not change
$ dumpsys connectivity trafficcontroller
....
     mIfaceIndexNameMap:
      ifaceIndex=5 ifaceName=ip6_vti0
      ifaceIndex=19 ifaceName=r_rmnet_data3
      ifaceIndex=17 ifaceName=r_rmnet_data1
      ifaceIndex=18 ifaceName=r_rmnet_data2
      ifaceIndex=23 ifaceName=wifi-aware0
....

$ dumpsys netstats
....
  BPF map content:
    ifaceIndex=5 ifaceName=ip6_vti0
    ifaceIndex=19 ifaceName=r_rmnet_data3
    ifaceIndex=17 ifaceName=r_rmnet_data1
    ifaceIndex=18 ifaceName=r_rmnet_data2
    ifaceIndex=8 ifaceName=rmnet_ipa0
....

Bug: 217624062
Test: dumpsys netstats, atest
com.android.server.net.BpfInterfaceMapUpdaterTest

Change-Id: If182bd97f72713b6347028668cf7bd4676b8aea4