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

service/server/server.pro

@@ -5,7 +5,7 @@ QT += core network remoteobjects
 equals(QT_MAJOR_VERSION, 6): QT += core5compat
 
 HEADERS = \
-        ../../client/utils.h \
+        ../../client/utilities.h \
         ../../ipc/ipc.h \
         ../../ipc/ipcserver.h \
         ../../ipc/ipcserverprocess.h \
@@ -15,7 +15,7 @@ HEADERS = \
         systemservice.h
 
 SOURCES = \
-        ../../client/utils.cpp \
+        ../../client/utilities.cpp \
         ../../ipc/ipcserver.cpp \
         ../../ipc/ipcserverprocess.cpp \
         localserver.cpp \