Avoid croniter infinite loop

[jlowin]

Summary

We thought we had identified all the weird DST issues with croniter, but a user recently stumbled across a new one. A simplified demo:

import pendulum
from croniter import croniter
from datetime import datetime

cron = croniter('0 0 * * 0', pendulum.datetime(2022, 8, 21, tz='America/Santiago'))
for i in range(10):
    print(cron.next(datetime))

Which results in

2022-08-28 00:00:00-04:00
2022-09-03 23:00:00-04:00
2022-09-03 23:00:00-04:00
2022-09-03 23:00:00-04:00
2022-09-03 23:00:00-04:00
2022-09-03 23:00:00-04:00
2022-09-03 23:00:00-04:00
2022-09-03 23:00:00-04:00
2022-09-03 23:00:00-04:00
2022-09-03 23:00:00-04:00

To avoid this (and others potentially lurking), this adds a check to see if we're stuck in a date loop when evaluating cron. If so, we exit the loop by creating a new cron instance that begins yielding immediately AFTER the date question.

Changes

Fixes a bug where certain DST conditions put schedules into an infinite loop

Importance

Checklist

This PR:

• adds new tests (if appropriate)
• adds a change file in the changes/ directory (if appropriate)
• updates docstrings for any new functions or function arguments, including docs/outline.toml for API reference docs (if appropriate)

[jawnsy]

LGTM