Fixes#1135. Adds enable check to certain to_string functions as some
std::array operations were ambiguous.
The addition of the capability to convert tuples to strings created an
ambiguity in the case std::array, which acts like a tuple and a
container. So it worked with the container conversion before, but could
also work with the new tuple conversion. And we didn't have any tests to
catch this.
This PR resolves the ambiguity, and adds some tests to check that array
is handled well.
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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
