Print heartbeat information in job dumpsys

Sample:
=======================
  Heartbeat:
    Current:    1
    Next
      ACTIVE:   0
      WORKING:  11
      FREQUENT: 43
      RARE:     130
    Last heartbeat: -1m21s575ms
    Next heartbeat: +9m38s425ms

Started users: [0, 10]
Registered 82 jobs:
  JOB #1000/800: 341134 android/com.android.server.pm.BackgroundDexOptService
       :
    Last run heartbeat: 1
    Ready: false (job=false user=true !pending=true !active=true !backingup=true comp=true)
=======================

Also:
=======================
    current_heartbeat=1
    next_heartbeat=[
      0
      11
      43
      130
    ]
    last_heartbeat_time=30828
    next_heartbeat_time=690828
  :
        last_run_heartbeat=1
=======================

Test: boot
Test: dumpsys jobscheduler
Test: incident_report jobscheduler
Change-Id: I2bf5d6e4189d3938e04a4790a6b1d55fb44f68e3