Add Significant Text agg to AggConfigs

[Dosant]

Summary

close #67394

This adds significant text aggregation to agg configs and expressions.

This aggregation is similar to significant terms but works only on fields of type TEXT. It also doesn't support child aggregations.
Agg docs

For now, I excluded this agg in visualize editor (everywhere where we excluded multi_terms), but we can consider enabling it, as it gives some user-facing value. For example, we can retrive significant terms from TEXT fields for tag cloud:

But since this agg doesn't support child aggregations it only works for the COUNT metric. If a user changes count to something else, then there is an error. So I suppose that more works needs to be done in visualize editor before we can enable those.

[Dosant]

Significant text aggregation only allows fields of types TEXT,
for this had to add a new way to filter supported fields for an aggregation.

With this we will also be able to allow integer fields for significant terms as mentioned here: #40368 (comment)

[Dosant]

@elasticmachine merge upstream

[elasticmachine]

Pinging @elastic/kibana-app-services (Team:AppServicesSv)

[ppisljar]

LGTM

[flash1293]

@elasticmachine merge upstream

[flash1293]

VisEditors changes LGTM, thanks for adding this. I will bring this topic up with the team, I agree that this is a helpful feature and should be exposed.

[Dosant]

@elasticmachine merge upstream

[kibana-ci]

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Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
data	506	508	+2

Public APIs missing comments

Total count of every public API that lacks a comment. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats comments for more detailed information.

id	before	after	diff
data	2930	2943	+13

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
data	441.0KB	444.8KB	+3.7KB
visTypeHeatmap	10.2KB	10.3KB	+60.0B
visTypeMetric	8.7KB	8.7KB	+20.0B
visTypePie	7.8KB	7.8KB	+40.0B
visTypeVislib	18.6KB	18.7KB	+40.0B
visTypeXy	40.9KB	41.1KB	+240.0B
total			+4.1KB

Unknown metric groups

API count

id	before	after	diff
data	3325	3340	+15

History

• 💔 Build #15887 failed de0f9dc
• 💚 Build #15609 succeeded 1ef1187
• 💚 Build #15439 succeeded 88edfd0
• 💔 Build #15426 failed aae5f28

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@elasticmachine merge upstream