Deprecate id_col argument to pt_cont_x

[kylebaron]

Summary

pt_cont_x() had an id_col argument that would let us count unique IDs. I don't think we want this behavior and would rather just count records summarized, which is actually the current behavior.

This PR deprecates that argument.

There is a simple test that checks that we can call these functions with no ID column. There are also existing regression tests that check that the output is consistent.

[kylebaron]

Thanks, @barrettk; we have open issue to fix tidyselect warnings that we'll do once these PRs are merged.