Fix Qt-RangeLoopDetach warnings in qmetaobjectpublisher.cpp

- introduce intermediate local const variables where it's required.

Axivion-Id: qt_Add-ons_qtwebchannel_dev_linux:SV28
Axivion-Id: qt_Add-ons_qtwebchannel_dev_linux:SV29
Axivion-Id: qt_Add-ons_qtwebchannel_dev_linux:SV30
Axivion-Id: qt_Add-ons_qtwebchannel_dev_linux:SV31
Axivion-Id: qt_Add-ons_qtwebchannel_dev_linux:SV32
Task-number: QTBUG-144780
Pick-to: 6.12
Change-Id: I4ec935b68964d91d25fe4c78f8d5206c7ffeb122
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>