Add dump of KeepaliveStatsTracker

To debug unexpected metrics values, print the built metrics into
the connectivity dump.

Sample of the added log dump:
KeepaliveStatsTracker enabled: true
   # android.net.connectivity.com.android.metrics.Dailykeepalive
InfoReported@3293424e
   automatic_keepalive_requests: 2
   distinct_user_count: 1
   duration_per_num_of_keepalive {
     duration_for_num_of_keepalive {
       keepalive_active_durations_msec: 36
       keepalive_registered_durations_msec: 36
       num_of_keepalive: 0
     }
     duration_for_num_of_keepalive {
       keepalive_active_durations_msec: 9
       keepalive_registered_durations_msec: 6
       num_of_keepalive: 1
     }
     duration_for_num_of_keepalive {
       keepalive_active_durations_msec: 7
       keepalive_registered_durations_msec: 10
       num_of_keepalive: 2
     }
   }
   keepalive_lifetime_per_carrier {
     keepalive_lifetime_for_carrier {
       active_lifetime_msec: 23
       carrier_id: -1
       intervals_msec: 10000
       lifetime_msec: 26
       transport_types: 1
     }
   }
   keepalive_requests: 2
   uid: 10097

Bug: 297292877
Test: adb shell dumpsys connectivity
Test: New test testDumpDoesNotCrash()
Change-Id: Ifc076a8dce734e9c175f1b1f28e1c448b9a792e5
3 files changed