Update series tests and example

[BNAndras]

No canonical tests were being used hence the almost complete overhaul. There is only one completion for this exercise to date so we won't break a whole lot here.

I implemented all the tests, but we can discuss that. Do we want the error validation tests? Should they be errors or should we return false values here.

I kept the expected argument order the same from before even though the problem specs has the series first and then the slice. Should we swap?

Does series:from-string make sense as a name? The tested property is slices so we can change it.

[github-actions]

This PR touches files which potentially affect the outcome of the tests of an exercise. This will cause all students' solutions to affected exercises to be re-tested.

If this PR does not affect the result of the test (or, for example, adds an edge case that is not worth rerunning all tests for), please add the following to the merge-commit message which will stops student's tests from re-running. Please copy-paste to avoid typos.

[no important files changed]

For more information, refer to the documentation. If you are unsure whether to add the message or not, please ping @exercism/maintainers-admin in a comment. Thank you!

[yurrriq]

I kept the expected argument order the same from before even though the problem specs has the series first and then the slice. Should we swap?

Given sublist(List1, Start, Len), I'd say aligning with the problem spec makes sense.

Of course it's questionably pedantic for such a simple exercise, but the updated example allocates some unnecessary lists and to me doesn't feel very idiomatic for the BEAM. Instead, I think we should prefer to stick closer to the Erlang example, though there we have the arguments swapped with respect to the problem spec.

Aside: The "slice" language is unfortunate as the documentation usually refers to such data as sublists, while strings:slice/2 carries a different meaning.