Add feature that shows next estimated cron executions

This is already added, but commented out.

There are a few edge cases regarding bad cron formats / cron formats far into the future that were causing the functionality to not work well, so it was commented out. The dependencies and code are still included in the comments.

+50 Internet Points

Locate the commented-out implementation and its retained dependencies in the repository, then read how cron expressions are parsed and displayed. Reproduce the bad-format and far-future cases described in the issue before deciding how the feature should behave. Done means next estimated executions are shown reliably for supported cron formats without breaking invalid or distant schedules.

Written by the indexing model from the issue text.