Easier cycling through dropdown_select options

[ajb]

cf https://github.com/dobtco/screendoor-v2/issues/3660#issue-155385956

When using keyboard shortcuts on the Responses page, it's easy to go from the last label / assignee to the first:

But it's more cumbersome for statuses, which use a native select:

(After making this GIF, I learned you can use Cmd + Up / Down for native selects, but that isn't really discoverable. Besides, the behavior on this page should be consistent.)

[ajb]

I think this is ready, although we need to ensure that we're not breaking expected accessibility behavior.