CHANGE(server): Extended user stats now requires Ban ACL

Previously, the Register ACL was required to get extended user
statistics (which includes used Mumble version, IP address etc.).
However, the Register ACL was deemed to be a rather arbitrary choice for
this. Instead, the Ban ACL was chosen as access to information such as
packet loss, IP address and used Mumble version and OS seem much more
relevant in the case of banning clients than it is for registering them.

Also, Ban permission is likely to be a better proxy for whether or not
someone is a moderator/admin on a given server than Register privilege.

Fixes #6697

src/murmur/Messages.cpp

@@ -2246,7 +2246,7 @@ void Server::msgUserStats(ServerUser *uSource, MumbleProto::UserStats &msg) {
 	const BandwidthRecord &bwr            = pDstServerUser->bwr;
 	const QList< QSslCertificate > &certs = pDstServerUser->peerCertificateChain();
 
-	bool extend = (uSource == pDstServerUser) || hasPermission(uSource, qhChannels.value(0), ChanACL::Register);
+	bool extend = (uSource == pDstServerUser) || hasPermission(uSource, qhChannels.value(0), ChanACL::Ban);
 
 	if (!extend && !hasPermission(uSource, pDstServerUser->cChannel, ChanACL::Enter)) {
 		PERM_DENIED(uSource, pDstServerUser->cChannel, ChanACL::Enter);