Events: Show user multiple location choices to disambiguate

[iandunn]

When a user types their city into the Events Widget, the API geocodes it to the best match. There's a lot of complexity involved in that, and the top result isn't the correct one too often.

Over the years we've spent a lot of time refining the API, see ​#meta5562 for the latest in a long string of tickets. I think the inherent problem is that we're trying to pick a single perfect result, which is just not practical.

Instead, we could ​return the top ~5 results, and let the user pick the one they intended.

That'd offer a better UX, and much more reliable results.