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/texteditor/codecchooser.cpp

@@ -28,7 +28,7 @@ CodecChooser::CodecChooser(Filter filter)
         std::find_if(mibs.begin(), mibs.end(), [](int n) { return n >=0; });
     if (firstNonNegative != mibs.end())
         std::rotate(mibs.begin(), firstNonNegative, mibs.end());
-    for (int mib : qAsConst(mibs)) {
+    for (int mib : std::as_const(mibs)) {
         if (filter == Filter::SingleByte && !isSingleByte(mib))
             continue;
         if (QTextCodec *codec = QTextCodec::codecForMib(mib)) {