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>