tools/rv: Allow rv list to filter for container

Add possibility to supply the container name to rv list:

  # rv list sched
  mon1
  mon2
  mon3

This lists only monitors in sched, without indentation.
Supplying -h, any option (string starting with -) or more than 1
argument will still print the usage.
Passing a non-existent container prints nothing and passing no container
continues to print all monitors, showing indentation for nested
monitors, reported after their container.

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/20250305140406.350227-10-gmonaco@redhat.com


Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>