Cleanup CLDR locale scripts

CLDR locale scripts may benefit from future cleanup after QTBUG-83488. Some possible areas:

• Decide on code style and use it consistently (black for suggested as formatter).
• Use xml.etree.ElementTree instead of custom xpath-like parser, also for emitting XML
• Don't use so many different unnamed tuples, perhaps use NamedTuple's for some of them and add type annotations were possible.