Added Iterable<Comparable> Extensions: .min and .max

[ChristianKleineidam]

I created .min and .max Iterable extensions. I used the fact that NaN != NaN to make the functions return the same results as the existing min() and max() functions.

See previous discussion at #42000 and #41902

[copybara-service]

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[copybara-service]

Thank you for your contribution. This project uses Gerrit for code reviews. Your pull request has automatically been converted into a code review at:

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[kevmoo]

@devoncarew @natebosch @lrhn – are we keeping these in pkg:collection – I could go either way here.

CC @mit-mit too

[natebosch]

Thanks for the PR.
I think we should keep these in package:collection.

https://pub.dev/documentation/collection/latest/collection/IterableComparableExtension.html