Fix incomplete Time.equals

Yes, `after`, `before` and `utcoffset` are constants currently. I included them anyway to not run into the same bug again in the near future.

I tried to put the comparisons in an order that's probably most efficient: stuff that's less likely to change to the back, most complicated stuff last.

[Bug: 65847](https://bugzilla.wikimedia.org/show_bug.cgi?id=65847)