Top Hits aggregation

[markov00]

Kibana version:
since 6.5

Describe the bug:
if you create a visualization with Top Hits as metric, the field list is not filtered.
The Top Hits aggregation, on visualization expect numbers. Only table accept also strings.
This will lead to some confusion by the user when trying to use top hits.

Steps to reproduce:

1. Create a piechart
2. Add a metric and select top hits as aggergation
3. The field dropdown will show a full list of fields for the selected index pattern.

Expected behavior:
The list should be filtered out to only the usable fields.

Screenshots:

Any additional context:

The issue is a regression introduced by this PR #22756

There is a small typo on the aggType filter where the we are looking for aggConfig.type.name !== 'top_hit' instead of top_hits in as the MetricAggType name reports. I think this can be the only cause of that problem

kibana/src/legacy/ui/public/agg_types/metrics/top_hit.js

Lines 42 to 50 in 78afde9

	if (aggConfig.type.name !== 'top_hit' || vis.type.name === 'table' || vis.type.name === 'metric') {
	return true;
	}
	return field.type === 'number';
	});
	export const topHitMetricAgg = new MetricAggType({
	name: 'top_hits',

[elasticmachine]

Pinging @elastic/kibana-app-arch

[markov00]

@ppisljar do you think my assumptions are right on the resolution of this issue?