[EPM] Send kibana version as query param to registry

[ruflin]

The Elastic Package Manager connects to the package registry to receive all the available packages. Inside each package is a definition with which versions of Kibana it is compatible. Then the package registry filters the packages based on the kibana version query param to only show the packages that are compatible with this Kibana version.

Currently Kibana does not send its own version as a query param: https://github.com/elastic/kibana/blob/master/x-pack/plugins/ingest_manager/server/services/epm/registry/index.ts#L36 This is not a problem at the moment as all the available packages are compatible with the current Kibana version but that might change in the future. Because of this a query param must be introduced.

[elasticmachine]

Pinging @elastic/ingest-management (Team:Ingest Management)

[jfsiii]

Just dropping a note that using a kbn-version header in the request is common in many parts if Kibana and required by some https://github.com/elastic/kibana/search?q=kbn-version&type=Code

Not sure whether to pick one or support both, but there is prior art for this.

[ruflin]

The /search API endpoint should not depend on headers specific to Kibana. It could also be the website or any consumer querying for packages for a specific Kibana version. Because of this it should be a query param and not a header.

[jfsiii]

Works for me

[skh]

Implemented in #71443