Documentation update for List class
Documentation update for List class

Documentation update, existing examples updated and added new ones.

Closes https://github.com/dart-lang/sdk/pull/47781
https://github.com/dart-lang/sdk/pull/47781

GitOrigin-RevId: b1f1683b63eb288fa49ce09f71796051f9dd66e1
Change-Id: I9ab5d0d0272c49e764fe58e1ef2f8045642411f7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/221400
Reviewed-by: Lasse Nielsen <80295e4ef244a07779f93eaa95d582bad8e316a5@google.com>
Commit-Queue: Lasse Nielsen <80295e4ef244a07779f93eaa95d582bad8e316a5@google.com>

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