WIP: Spawn backend plugins v2 (#19835)

* 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

pkg/setting/setting.go

@@ -206,6 +206,7 @@ var (
 	S3TempImageStoreSecretKey string
 
 	ImageUploadProvider string
+	FeatureToggles      map[string]bool
 )
 
 // TODO move all global vars to this struct
@@ -955,6 +956,7 @@ func (cfg *Cfg) Load(args *CommandLineArgs) error {
 	for _, feature := range util.SplitString(featuresTogglesStr) {
 		cfg.FeatureToggles[feature] = true
 	}
+	FeatureToggles = cfg.FeatureToggles
 
 	// check old location for this option
 	if panelsSection.Key("enable_alpha").MustBool(false) {