metrics: Simplify Wattson hierarchy output

Shift from a recursively and generically defined rail and subrail
estimate into one that is explicitly defined. This cleans up the output
to be more readable and simpler. The new format is also easier and more
intuitive to parse with traditional protobuf/JSON parsers.

This requires that the hierarchy be explicitly defined in
wattson_in_time_period.proto, and for the same proto file to maintain a
superset (from all configurations of all possible devices) of all
hierarchies.

Before:
rail {
  name: "cpu_subsystem"
  estimate_mw: 42.126297
  rail {
    name: "DSU_SCU"
    estimate_mw: 7.404674
  }
  rail {
    name: "policy0"
    estimate_mw: 34.721622
    rail {
      name: "cpu0"
      estimate_mw: 10.706565
    }
    rail {
      name: "cpu1"
      estimate_mw: 8.314949
    }
    rail {
      name: "cpu2"
      estimate_mw: 7.7762628
    }
    rail {
      name: "cpu3"
      estimate_mw: 7.9238434
    }
  }
}

After:
cpu_subsystem {
  estimate_mw: 42.126297
  policy0 {
    estimate_mw: 34.721622
    cpu0 {
      estimate_mw: 10.706565
    }
    cpu1 {
      estimate_mw: 8.314949
    }
    cpu2 {
      estimate_mw: 7.7762628
    }
    cpu3 {
      estimate_mw: 7.9238434
    }
  }
  dsu_scu {
    estimate_mw: 7.404674
  }
}

Test: tools/diff_test_trace_processor.py out/linux/trace_processor_shell --name-filter '.*wattson.*'
Bug: 352627297
Change-Id: I58da720a5d8982b5fcd9eb16c24099fe4de3c419