tools/rv: Add in-kernel monitor interface

Add the ability to control and trace in-kernel monitors. This is
a generic interface, it will check for existing monitors and enable
standard setup, like enabling reactors.

For example:

  # rv list
  wip                      wakeup in preemptive per-cpu testing monitor. [OFF]
  wwnr                     wakeup while not running per-task testing model. [OFF]

  # rv mon wwnr --help
  rv version 6.1.0-rc4: help

  usage: rv mon wwnr [-h] [-q] [-r reactor] [-s] [-v]
	-h/--help: print this menu and the reactor list
	-r/--reactor 'reactor': enables the 'reactor'
	-s/--self: when tracing (-t), also trace rv command
	-t/--trace: trace monitor's event
	-v/--verbose: print debug messages

  available reactors: nop printk panic

  # rv mon wwnr --trace
          <TASK>-PID      [CPU]  TYPE       ID                    STATE x EVENT                    -> NEXT_STATE               FINAL
              |   |          |     |        |                        |     |                           |                       |
              rv-3613     [001] event     3613                  running x switch_out               -> not_running              Y
            sshd-1248     [005] event     1248                  running x switch_out               -> not_running              Y
          <idle>-0        [005] event       71              not_running x wakeup                   -> not_running              Y
          <idle>-0        [005] event       71              not_running x switch_in                -> running                  N
      kcompactd0-71       [005] event       71                  running x switch_out               -> not_running              Y
          <idle>-0        [000] event      860              not_running x wakeup                   -> not_running              Y
          <idle>-0        [000] event      860              not_running x switch_in                -> running                  N
    systemd-oomd-860      [000] event      860                  running x switch_out               -> not_running              Y
          <idle>-0        [000] event      860              not_running x wakeup                   -> not_running              Y
          <idle>-0        [000] event      860              not_running x switch_in                -> running                  N
    systemd-oomd-860      [000] event      860                  running x switch_out               -> not_running              Y
          <idle>-0        [005] event       71              not_running x wakeup                   -> not_running              Y
          <idle>-0        [005] event       71              not_running x switch_in                -> running                  N
      kcompactd0-71       [005] event       71                  running x switch_out               -> not_running              Y
          <idle>-0        [000] event      860              not_running x wakeup                   -> not_running              Y
          <idle>-0        [000] event      860              not_running x switch_in                -> running                  N
    systemd-oomd-860      [000] event      860                  running x switch_out               -> not_running              Y
          <idle>-0        [001] event     3613              not_running x wakeup                   -> not_running              Y

Link: https://lkml.kernel.org/r/1e57547e3acadda6e23949b2672c89e76ec2ec42.1668180100.git.bristot@kernel.org



Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>