Remove unordered outputs in v4

[ajfriend]

h3.api.basic_str (the default) and h3.api.basic_int have many functions which return "unordered" results in the form of a Python set. The original intention for this was to signal to the user that there was no guarantee of the ordering of the outputs.

However, set is a little less ergonomic than list: you can't do out[0] to get the first element. Also, there is no matching "unordered" output for h3.api.numpy_int or h3.api.memview_int.

Also, we may have future versions of the library output results in "canonical" order, which would require a list output. Since this would be a breaking change, we'll introduce it in v4.