Config: making [aws][external_id] part of env (#72062)

* Config: making [aws][external_id] part of env

* Fix go.sum

* Add a test

pkg/services/pluginsintegration/config/config.go

@@ -34,6 +34,7 @@ func ProvideConfig(settingProvider setting.Provider, grafanaCfg *setting.Cfg, fe
 		allowedUnsigned,
 		allowedAuth,
 		aws.KeyValue("assume_role_enabled").MustBool(grafanaCfg.AWSAssumeRoleEnabled),
+		aws.KeyValue("external_id").Value(),
 		grafanaCfg.Azure,
 		grafanaCfg.SecureSocksDSProxy,
 		grafanaCfg.BuildVersion,