Add new set of max job counts.

We'll use different max numbers for screen on and screen off,
and the semantics will be different from that of P (since the previous
code was broken), so I'm just adding a new set of configs.

Also add wrapper classes for config values.

Bug: 111360323
Test: dumpsys jobscheduler contains the following sections.
  max_job_total_on_normal=4
  max_job_bg_on_normal=2
  max_job_total_on_moderate=4
  max_job_bg_on_moderate=1
  max_job_total_on_low=4
  max_job_bg_on_low=1
  max_job_total_on_critical=2
  max_job_bg_on_critical=1
  max_job_total_off_normal=8
  max_job_bg_off_normal=4
  max_job_total_off_moderate=6
  max_job_bg_off_moderate=4
  max_job_total_off_low=4
  max_job_bg_off_low=1
  max_job_total_off_critical=2
  max_job_bg_off_critical=1

Change-Id: I46004a1633494c0498681f4ee1d0045d3c3ab4d7