fix(ui): advise users on correct chron syntax for scheduling

[kevinkarchacryl]

We recently added backend support for more advanced cron syntax. For example, to schedule ingestion on the 2nd Monday of every month you could do either "0 0 0 0 1#2" or "0 0 8-14 0 1". However, only the 2nd method is supported on the frontend. For example, when using the hashmark syntax, if you switch in and out of the advanced tab it will get erased:



But when using the other syntax, everything works:

Long story short: this is because the frontend uses two different libraries for cron: one that supports # and one that doesn't. I think these code changes are an acceptable alternative but I'm open to other ideas. The test I added is just for the backend to make sure both ways work.
With my changes, the user will not able to uncheck the advanced box if they use the hashmark. This is what you see when you put a hashmark in the schedule:

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub

[codecov]

Codecov Report

Attention: Patch coverage is 12.50000% with 28 lines in your changes missing coverage. Please review.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...c/app/ingest/source/builder/CreateScheduleStep.tsx	12.50%	28 Missing ⚠️

❌ Your patch check has failed because the patch coverage (12.50%) is below the target coverage (75.00%). You can increase the patch coverage or adjust the target coverage.

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