migrated the codebase to Qt6 and fixed some compatibility issues

* used a Qt6 ported version of SortFilterProxyModel
* used an updated Qt6 compatible version of QXZing
* added a flag to windows linker to avoid WinMain problem of MSVCRTD
* renamed utils.cpp to utilities.cpp for avoiding confusion with the same file name in SortFilterProxyModel

client/configurators/ikev2_configurator.cpp

@@ -13,7 +13,7 @@
 #include "core/server_defs.h"
 #include "containers/containers_defs.h"
 #include "core/scripts_registry.h"
-#include "utils.h"
+#include "utilities.h"
 
 Ikev2Configurator::ConnectionData Ikev2Configurator::prepareIkev2Config(const ServerCredentials &credentials,
     DockerContainer container, ErrorCode *errorCode)

client/configurators/openvpn_configurator.cpp

@@ -10,7 +10,7 @@
 #include "core/server_defs.h"
 #include "containers/containers_defs.h"
 #include "core/scripts_registry.h"
-#include "utils.h"
+#include "utilities.h"
 
 #include <openssl/rsa.h>
 #include <openssl/x509.h>

client/configurators/ssh_configurator.cpp

@@ -12,7 +12,7 @@
 #include <qtimer.h>
 
 #include "core/server_defs.h"
-#include "utils.h"
+#include "utilities.h"
 
 using namespace QSsh;
 
@@ -59,7 +59,7 @@ void SshConfigurator::openSshTerminal(const ServerCredentials &credentials)
 {
 #ifndef Q_OS_IOS
     QProcess *p = new QProcess();
-    p->setReadChannelMode(QProcess::SeparateChannels);
+    p->setProcessChannelMode(QProcess::SeparateChannels);
 
 #ifdef Q_OS_WIN
     p->setProcessEnvironment(prepareEnv());

client/configurators/vpn_configurator.cpp

@@ -10,7 +10,7 @@
 #include <QJsonDocument>
 
 #include "containers/containers_defs.h"
-#include "utils.h"
+#include "utilities.h"
 
 Settings &VpnConfigurator::m_settings()
 {

client/configurators/wireguard_configurator.cpp

@@ -16,7 +16,7 @@
 #include "core/server_defs.h"
 #include "containers/containers_defs.h"
 #include "core/scripts_registry.h"
-#include "utils.h"
+#include "utilities.h"
 
 WireguardConfigurator::ConnectionData WireguardConfigurator::genClientKeys()
 {