The time-zone script was importing two functions from the locale data
generation script. Move them to a separate module, to which I'll
shortly add some more shared utilities. Cleaned up some imports in the
process.
Combined qlocalexml2cpp's and xpathlit's error classes into a new
Error class in the new module and made it a bit more like a proper
python error class.
Task-number: QTBUG-81344
Change-Id: Idbe0139ba9aaa2f823b8f7216dee1d2539c18b75
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>
