* WIP: Spawn backend plugins v2

* Add test for plugin version

* Fix support for SDK plugins

Co-authored-by: Kyle Brandt <kyle@kbrandt.com>
Co-authored-by: Marcus Olsson <olsson.e.marcus@gmail.com>
Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>

* WIP: Draft PR for fork of V2 sdk / bi-directional support (#19890)

* temporary use export-datasource-plugin branch of grafana-plugin-sdk

* fix failing test

* remove debug (spew) lines

* misc cleanup

* add expressions feature toggle

* use latest grafana-plugin-sdk-go