Plugins: Add file store abstraction for handling plugin files (#65432)

* add file store

* fix markdown fetch bug

* add markdown tests

* fix var name

pkg/services/pluginsintegration/pluginsintegration.go

@@ -10,6 +10,7 @@ import (
 	"github.com/grafana/grafana/pkg/plugins/config"
 	"github.com/grafana/grafana/pkg/plugins/manager"
 	"github.com/grafana/grafana/pkg/plugins/manager/client"
+	"github.com/grafana/grafana/pkg/plugins/manager/filestore"
 	"github.com/grafana/grafana/pkg/plugins/manager/loader"
 	"github.com/grafana/grafana/pkg/plugins/manager/loader/assetpath"
 	"github.com/grafana/grafana/pkg/plugins/manager/loader/finder"
@@ -60,6 +61,8 @@ var WireSet = wire.NewSet(
 	sources.ProvideService,
 	pluginSettings.ProvideService,
 	wire.Bind(new(pluginsettings.Service), new(*pluginSettings.Service)),
+	filestore.ProvideService,
+	wire.Bind(new(plugins.FileStore), new(*filestore.Service)),
 )
 
 // WireExtensionSet provides a wire.ProviderSet of plugin providers that can be