runtime: Pass SELinux policy for containers to the agent

Pass SELinux policy for containers to the agent if `disable_guest_selinux`
is set to `false` in the runtime configuration. The `container_t` type
is applied to the container process inside the guest by default.
Users can also set a custom SELinux policy to the container process using
`guest_selinux_label` in the runtime configuration. This will be an
alternative configuration of Kubernetes' security context for SELinux
because users cannot specify the policy in Kata through Kubernetes's security
context. To apply SELinux policy to the container, the guest rootfs must
be CentOS that is created and built with `SELINUX=yes`.

Fixes: #4812

Signed-off-by: Manabu Sugimoto <Manabu.Sugimoto@sony.com>

src/runtime/pkg/katautils/config_test.go

@@ -554,6 +554,7 @@ func TestMinimalRuntimeConfig(t *testing.T) {
 		VhostUserStorePath:    defaultVhostUserStorePath,
 		VirtioFSCache:         defaultVirtioFSCacheMode,
 		BlockDeviceAIO:        defaultBlockDeviceAIO,
+		DisableGuestSeLinux:   defaultDisableGuestSeLinux,
 	}
 
 	expectedAgentConfig := vc.KataAgentConfig{