multi: move routing.TlvTrafficShaper => htlcswitch.AuxTrafficShaper

With this commit we move the traffic shaper definition from the routing
package to the HTLC switch package as a preparation for being able to
use it there as well.
At the same time we rename it to AuxTrafficShaper to be more in line
with the other auxiliary components.

routing/bandwidth_test.go

@@ -118,7 +118,9 @@ func TestBandwidthManager(t *testing.T) {
 			m, err := newBandwidthManager(
 				g, sourceNode.pubkey, testCase.linkQuery,
 				fn.None[[]byte](),
-				fn.Some[TlvTrafficShaper](&mockTrafficShaper{}),
+				fn.Some[htlcswitch.AuxTrafficShaper](
+					&mockTrafficShaper{},
+				),
 			)
 			require.NoError(t, err)