Introduce and use Utils::stripAccelerator

src/libs/utils/stringutils.cpp

src/libs/utils/stringutils.h

src/plugins/coreplugin/actionmanager/command.cpp

src/plugins/coreplugin/dialogs/ioptionspage.cpp

src/plugins/coreplugin/dialogs/readonlyfilesdialog.cpp

src/plugins/coreplugin/locator/commandlocator.cpp

src/plugins/designer/settingspage.cpp

tests/auto/utils/stringutils/tst_stringutils.cpp