Plugins: Use grafana-plugin-sdk-go v0.5.0 (#21116)

* fix dispense

* plugin loading refactor

Moves common functionality of registering, starting,
stopping and restarting backend plugins to
backendplugin package.

* simplify plugin descriptors

* target sdk v0.5.0

Co-authored-by: Kyle Brandt <kyle@kbrandt.com>

pkg/plugins/renderer_plugin.go

@@ -1,11 +1,22 @@
 package plugins
 
-import "encoding/json"
+import (
+	"context"
+	"encoding/json"
+	"path"
+
+	pluginModel "github.com/grafana/grafana-plugin-model/go/renderer"
+	"github.com/grafana/grafana/pkg/infra/log"
+	"github.com/grafana/grafana/pkg/plugins/backendplugin"
+	"github.com/grafana/grafana/pkg/util/errutil"
+	plugin "github.com/hashicorp/go-plugin"
+)
 
 type RendererPlugin struct {
 	PluginBase
 
 	Executable string `json:"executable,omitempty"`
+	GrpcPlugin pluginModel.RendererPlugin
 }
 
 func (r *RendererPlugin) Load(decoder *json.Decoder, pluginDir string) error {
@@ -17,6 +28,36 @@ func (r *RendererPlugin) Load(decoder *json.Decoder, pluginDir string) error {
 		return err
 	}
 
+	cmd := ComposePluginStartCommmand("plugin_start")
+	fullpath := path.Join(r.PluginDir, cmd)
+	descriptor := backendplugin.NewRendererPluginDescriptor(r.Id, fullpath)
+	if err := backendplugin.Register(descriptor, r.onPluginStart); err != nil {
+		return errutil.Wrapf(err, "Failed to register backend plugin")
+	}
+
 	Renderer = r
 	return nil
 }
+
+func (r *RendererPlugin) Start(ctx context.Context) error {
+	if err := backendplugin.StartPlugin(ctx, r.Id); err != nil {
+		return errutil.Wrapf(err, "Failed to start renderer plugin")
+	}
+
+	return nil
+}
+
+func (r *RendererPlugin) onPluginStart(pluginID string, client *plugin.Client, logger log.Logger) error {
+	rpcClient, err := client.Client()
+	if err != nil {
+		return err
+	}
+
+	raw, err := rpcClient.Dispense(pluginID)
+	if err != nil {
+		return err
+	}
+
+	r.GrpcPlugin = raw.(pluginModel.RendererPlugin)
+	return nil
+}