fix: issue2551278 - datetime.datetime.utcnow deprecation. We now use the timezone aware utc dates for python 3.11+. But we have to make all the rest of the dates (datetime.min, unix epoch date) timezon aware so we can subtract them. Also need to marshall/unmarshall timezone aware iso formatted date strings.

[run]

# ignore the dist utils. They are not part of the code base
# we are going to test. They are used by maintainers only.
omit = roundup/dist/*