Plugins: Add synchronous CDN plugin loader (#99096)

* WIP

* Run plugin validations and validation steps sequentially if feature is off

* Remove dependency between sources.Service and pluginscdn.Service

* lint

* Parallelize validation only if class is CDN

* re-generate feature toggles

* remove waitgroup usage

* PR review: Add loader concurrency limit setting

* re-generate feature toggles

* pr review feedback

* fix const name

* Skip module.js validation for cdn plugins

* do not run validation steps in parallel

* lint

* reduce diff

* re-generate feature toggles

* lint

* pr review feedback

* remove leftover config.PluginManagementCfg from sources.Service

pkg/services/pluginsintegration/renderer/renderer.go

@@ -141,5 +141,5 @@ func createLoader(cfg *config.PluginManagementCfg, pluginEnvProvider envvars.Pro
 
 	et := pluginerrs.ProvideErrorTracker()
 
-	return loader.New(d, b, v, i, t, et), nil
+	return loader.New(cfg, d, b, v, i, t, et), nil
 }