Make the IEnumerable max depth for actual and expected output configurable

[andre-ss6]

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Currently, the max depth for printing actual and expected IEnumerables is hardcoded as 5, even at v3 (though v3 is at least referencing the const fields).

It's kinda frustrating to have to debug a thery every time in order to know which specific test failed.

[andre-ss6]

I'm up for contributing with this, I just need to know the design decisions (will it be configurable programmatically or via configuration file? or both? or an overload for Asserts, perhaps?).

By the way, I think 5 is a quite low number anyway. Perhaps the default could be higher.