Make support for single-use iterables explicit

[ikappaki]

Hi,

could you please consider patch to remove explicit support of single-use iterables in sequences. It fixes #1192.

single-use iterables now throw a TypeError, when they are implicitly or explicitly coerced into a sequence. A new iterator-seq is introduced to explicitly convert them into a seq instead . See #1198 (comment) for the rationale.

The count fn was also updated to behave the same.

There were a few places where single use iterators were converted implicitly to a seq, which are now explicitly converted using a iterator-seq or the python equivalent instead.

Tests are added for the same, as well as documentation section under Python Iterators.

Thanks

[chrisrink10]

Thank you for the very thoughtful conversation and analysis in #1198 and for the PR @ikappaki

This looks very nice. I have a couple of very minor comments, but I think this looks good overall and I'm glad to get this merged in.