Allow missing buckets for non-string fields

[flash1293]

Right now missing bucket only works for string fields:

kibana/src/plugins/data/common/search/aggs/buckets/terms.ts

Line 174 in 8cb3dbc

if (agg.params.missingBucket && agg.params.field.type === 'string') {

However it would be helpful to be able to use this feature for other field type as well. I suggest we change the implementation of how missing bucket works - instead of using the missing param on Elasticsearch side, it becomes a special case of the "other bucket" logic (requesting NOT <field name>: *)

Requested here: #102640

[elasticmachine]

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

[elasticmachine]

Pinging @elastic/kibana-visualizations @elastic/kibana-visualizations-external (Team:Visualizations)

[markov00]

In order to provide better transparency of priorities, issues that will not be prioritized within the next 24 months are being closed.

Tracking request in Lens general improvements ice box #184459