[Telemetry] Kibana config usage schema

[Bamieh]

Currently config usage collector schema is excluded from the mapping json files.

This decision was intentional since explicitly typing every config in the collector schema is not practical for devs and adds a lot of maintenance time on the core team.

We'll be experimenting with flattened_type ES type and runtime fields to query this collector. Both are not yet supported by the collection schema types.

If we find flattened_type enough for this use case we would need to support this type in our telemetry tooling. Otherwise if we had to explicitly specify every kibana config in the schema we'd need to improve our telemetry tools to automatically do this for devs. Although flattened_type seems promising enough for this use case.

[elasticmachine]

Pinging @elastic/kibana-core (Team:Core)

[elasticmachine]

Pinging @elastic/kibana-telemetry (Team:KibanaTelemetry)

[lukeelmers]

We will close this for now -- if we get feedback from any teams that are interested in using flattened_type, we can re-open or create a new issue. But at the moment, we are not aware of anyone that needs this.