Port from qAsConst() to std::as_const()

We've been requiring C++17 since Qt 6.0, and our qAsConst use finally
starts to bother us (QTBUG-99313), so time to port away from it
now.

Since qAsConst has exactly the same semantics as std::as_const (down
to rvalue treatment, constexpr'ness and noexcept'ness), there's really
nothing more to it than a global search-and-replace.

Task-number: QTBUG-99313
Change-Id: I88edd91395849574436299b8badda21bb93bea39
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/threadshandler.cpp

@@ -301,7 +301,7 @@ bool ThreadsHandler::notifyGroupExited(const QString &groupId)
         if (item->threadData.groupId == groupId)
             list.append(item);
     });
-    for (ThreadItem *item : qAsConst(list))
+    for (ThreadItem *item : std::as_const(list))
         destroyItem(item);
 
     m_pidForGroupId.remove(groupId);