chore(protocol): only allow enc. password changes on cluster config (#10145)

In practice we already always call SetPassword and ClusterConfig
together. However it's not just "sensible" to do that, it's required: If
the passwords change, the remote device needs to know about that to
check that the enc. setup is valid/consistent (e.g. tokens match,
folder-type is appropriate, ...).
And with the passwords set later, there's no point in adding them as
part of creating a new connection.

This is a "followup" (if one can call it that 4 years later :) ) to
resp. fix for the following commit:
924b96856f

Co-authored-by: Jakob Borg <jakob@kastelo.net>

lib/model/model_test.go

@@ -2969,7 +2969,7 @@ func TestConnCloseOnRestart(t *testing.T) {
 	nw := &testutil.NoopRW{}
 	ci := &protocolmocks.ConnectionInfo{}
 	ci.ConnectionIDReturns(srand.String(16))
-	m.AddConnection(protocol.NewConnection(device1, br, nw, testutil.NoopCloser{}, m, ci, protocol.CompressionNever, nil, m.keyGen), protocol.Hello{})
+	m.AddConnection(protocol.NewConnection(device1, br, nw, testutil.NoopCloser{}, m, ci, protocol.CompressionNever, m.keyGen), protocol.Hello{})
 	m.mut.RLock()
 	if len(m.closed) != 1 {
 		t.Fatalf("Expected just one conn (len(m.closed) == %v)", len(m.closed))
@@ -3628,11 +3628,11 @@ func testConfigChangeTriggersClusterConfigs(t *testing.T, expectFirst, expectSec
 	cc1 := make(chan struct{}, 1)
 	cc2 := make(chan struct{}, 1)
 	fc1 := newFakeConnection(device1, m)
-	fc1.ClusterConfigCalls(func(_ *protocol.ClusterConfig) {
+	fc1.ClusterConfigCalls(func(_ *protocol.ClusterConfig, _ map[string]string) {
 		cc1 <- struct{}{}
 	})
 	fc2 := newFakeConnection(device2, m)
-	fc2.ClusterConfigCalls(func(_ *protocol.ClusterConfig) {
+	fc2.ClusterConfigCalls(func(_ *protocol.ClusterConfig, _ map[string]string) {
 		cc2 <- struct{}{}
 	})
 	m.AddConnection(fc1, protocol.Hello{})