remove 'No results found' treatment for single count visualization

[tsullivan]

Addresses: #3682 (count and unique count widget)

[tbragin]

Addresses issue #3682

LGTM, functionally

[lukasolson]

Yeah, unfortunately, this has a lot of side effects. One example is the table vis type, which is completely empty if there are no results. Also, date histograms still show "no results found."

I think we should try to make a change that's limited in scope to modifying the metric vis to show "0" when there are no results, and only when the metric agg is set to "count" or "unique count".

[tsullivan]

@lukasolson I updated the PR and the screenshots. Now I'm having only the metric vis type modified (table and date histogram vis are untouched). It's shows a "no data available" message if it encounters something with no readable value.

Assuming I am on the right track now, before this is merged, I'd like to discuss how to remove some repetition of code from visualize.html - I'd like to have a single flag to check in the scope that holds the value of vis.type.requiresSearch && esResp.hits.total === 0 && vis.type.name !== 'metric'

[lukasolson]

Yeah, this looks good, and I agree that it makes sense to have a value in scope instead of checking all three of those values each time.

LGTM.

[tsullivan]

After rebasing this branch, the feature is not testing out as well as it used to. It has new buggy behavior where it'll throw an error for certain kinds of metric aggregations if the result count is 0.

[tsullivan]

Closing this for the same reason as #5253. It's not such a low fruit, it needs more attention