internal/distro/rhel8/edge: add sos package for rhel8.6+ and CS8

Similarly to the change made for rhel9, adding the sos package
gives users a built-in way to gather system logs and debug info.

Signed-off-by: Irene Diez <idiez@redhat.com>

internal/distro/rhel8/edge.go

@@ -242,6 +242,7 @@ func edgeCommitPackageSet(t *imageType) rpmmd.PackageSet {
 				"fdo-client",
 				"fdo-owner-cli",
 				"greenboot-default-health-checks",
+				"sos",
 			},
 		})
 	}