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/coreplugin/statusbarmanager.cpp

@@ -91,7 +91,7 @@ static void createStatusBarManager()
         delete statusContext;
         // This is the catch-all on rampdown. Individual items may
         // have been removed earlier by destroyStatusBarWidget().
-        for (const QPointer<IContext> &context : qAsConst(m_contexts)) {
+        for (const QPointer<IContext> &context : std::as_const(m_contexts)) {
             ICore::removeContextObject(context);
             delete context;
         }