fix: xml report iteration failure

[tommasobertoni]

The context iterator is an ElementTree.IterParseIterator instance and does not expose a next() method.
The fix uses the __next__() method instead.

Additionally:

• remove import codecs and import re as unused
• define _XmlIterator for type hinting

Fixes #300.

[tommasobertoni]

@microsoft-github-policy-service agree company="Bending Spoons"

[tommasobertoni]

Hi @xinyuwen2 👋🏻 are you able to take a look? 🙏🏻