ClassView: Optimize operator== of internal data

Make all of the fields of SymbolLocation and SymbolInformation
const members. Optimize a bit operator== of these structures:
check first if hashes are non-equal - in this case return
false early. Fix hash type of SymbolInformation for porting
to Qt6 purpose.

Task-number: QTCREATORBUG-25317
Task-number: QTCREATORBUG-24098
Change-Id: I769f99ff3157093e9f10ee3929bc7f6eb83f34e3
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/classview/classviewparser.cpp

@@ -479,6 +479,7 @@ void Parser::requestCurrentState()
 {
     d->timer.stop();
 
+    // TODO: we need to have a fresh SessionManager data here, which we could pass to parse()
     const ParserTreeItem::ConstPtr newRoot = parse();
     {
         QWriteLocker locker(&d->rootItemLocker);