[MM-40179] Go into directories when trying to export attachments (#19249)

* MM-40179 traverse directories when trying to export

* fix test

* fix s3 to behabe the same way

* add test for paths way too deep

* test recursion only on localstorage

* make list directories non recursively the default approach

* fix linting error

* fix non-recursive case

Co-authored-by: = <=>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/plugin.go

@@ -823,7 +823,7 @@ func (ch *Channels) notifyPluginEnabled(manifest *model.Manifest) error {
 }
 
 func (ch *Channels) getPluginsFromFolder() (map[string]*pluginSignaturePath, *model.AppError) {
-	fileStorePaths, appErr := ch.srv.listDirectory(fileStorePluginFolder)
+	fileStorePaths, appErr := ch.srv.listDirectory(fileStorePluginFolder, false)
 	if appErr != nil {
 		return nil, model.NewAppError("getPluginsFromDir", "app.plugin.sync.list_filestore.app_error", nil, appErr.Error(), http.StatusInternalServerError)
 	}