Add __iter__ method to TracedCursorProxy (#4427)

* Add iter to TracedCursorProxy

* Add test to verify cursor is iterable

* Disable linter rule for dbapi iter test

* Add __iter__ to MockCursor

* Add mysql docker tests

* Push linter fixes

* Update docs-requirements.txt

* Update CHANGELOG.md

* Update nitpick-exceptions.ini

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Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>