Consolidate list-like checking to is_list_like
Closes https://github.com/pydata/pandas/issues/11740

Let me know what tests would be helpful for these types of 'cleaning' PRs, and whether a "what's new" is needed.

@kawochen green. 
In the end, I'm not sure it's much simpler, although it is a bit more encapsulated & explicit
Let me know your thoughts
 @MaximilianR update?
 Yup, on it. Aiming for this w/e.
 closing, but pls reopen if working on it
 OK, apologies for letting this drop.
 np again. your contributions are great! just trying to move things forward.
