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/protocol/benchmark_test.go

@@ -64,14 +64,14 @@ func benchmarkRequestsTLS(b *testing.B, conn0, conn1 net.Conn) {
 
 func benchmarkRequestsConnPair(b *testing.B, conn0, conn1 net.Conn) {
 	// Start up Connections on them
-	c0 := NewConnection(LocalDeviceID, conn0, conn0, testutil.NoopCloser{}, new(fakeModel), new(mockedConnectionInfo), CompressionMetadata, nil, testKeyGen)
+	c0 := NewConnection(LocalDeviceID, conn0, conn0, testutil.NoopCloser{}, new(fakeModel), new(mockedConnectionInfo), CompressionMetadata, testKeyGen)
 	c0.Start()
-	c1 := NewConnection(LocalDeviceID, conn1, conn1, testutil.NoopCloser{}, new(fakeModel), new(mockedConnectionInfo), CompressionMetadata, nil, testKeyGen)
+	c1 := NewConnection(LocalDeviceID, conn1, conn1, testutil.NoopCloser{}, new(fakeModel), new(mockedConnectionInfo), CompressionMetadata, testKeyGen)
 	c1.Start()
 
 	// Satisfy the assertions in the protocol by sending an initial cluster config
-	c0.ClusterConfig(&ClusterConfig{})
-	c1.ClusterConfig(&ClusterConfig{})
+	c0.ClusterConfig(&ClusterConfig{}, nil)
+	c1.ClusterConfig(&ClusterConfig{}, nil)
 
 	// Report some useful stats and reset the timer for the actual test
 	b.ReportAllocs()