Update apparmor profile to support v4.0.0

AppArmor v4.0.0 introduced podman, runc and crun profiles for
/usr/bin/podman, /usr/sbin/runc and /usr/bin/crun respectively[1]. This
change breaks the stopping of containers, because the built-in profile
assigned to containers doesn't accept signals from podman, runc and
crun peers.

This change extends the default profile with rules that allow receiving
signals from processes that run confined with the podman, runc or crun
profile. It is backward compatible because the peer value is a regular
expression (AARE) so the referenced profile doesn't have to exist for
this profile to successfully compile and load.

The signal set from runc or crun remains unconstrained as the user can
issue any signal via the kill sub-command of podman.

Signals from podman itself are restricted to the common interrupt and
termination signals.

Closes #1898

[1] https://gitlab.com/apparmor/apparmor/-/commit/2594d936

Signed-off-by: Neil Wilson <neil@aldur.co.uk>

pkg/apparmor/apparmor_linux_template.go

@@ -21,6 +21,10 @@ profile {{.Name}} flags=(attach_disconnected,mediate_deleted) {
   # Allow signals from privileged profiles and from within the same profile
   signal (receive) peer=unconfined,
   signal (send,receive) peer={{.Name}},
+  # Allow certain signals from OCI runtimes (podman, runc and crun)
+  signal (receive) peer={/usr/bin/,/usr/sbin/,}runc,
+  signal (receive) peer={/usr/bin/,/usr/sbin/,}crun,
+  signal (receive) set=(int, quit, kill, term) peer={/usr/bin/,/usr/sbin/,}podman,
 {{end}}
 
   deny @{PROC}/* w,   # deny write for all files directly in /proc (not in a subdir)