MM-16261: Synchronize plugins in HA (#11657)

* MM-16272 - Synchronize plugins across cluster (#11611)

* MM-16272 - Synchronize plugins across cluster

* Adding a test

* MM-16272 - Fixed tests

* MM-16272 - PR feedback

* MM-16270 - Plugin Sync (#11615)

* Initial implementation for plugin synch with file store. WIP

* Removed ListAll implementation. Used ListDirectory and change localstore to be consistent and return all items (files and folders) from directory

* Refactored plugin filestore operations out of main install/remove plugin

* Fixing error handling details

* Changes to use structured logging

* More logging fixes

* Wording and comments improvements

* Error handling and control flow improvements

* Changed managed flag check to use os.stat

* Added file store plugin dir and filename consts

* Replaced FileRead to use a the FileReader in PluginSync

* Minor styling and PR feedback changes

* Minor error handling improvements

* Added unit test for SyncPlugins. Changed SyncPlugins to use plugins environment to list available plugins

* PR Feedback improvements

* Minor err handling fix

* Removing FileStorePath from PluginEventData (#11644)

* Fix plugin path (#11654)

* tweak path, logging

Fix an issue not finding the plugins folder in S3. Tweak logging messages to add additional clarity.

* Removing FileExists check when Syncing plugins. Updated localstore to not return an error when directory does not exist

* PR Feedback

* Install prepackaged plugins locally only (#11656)

* s/uninstall/remove

* Updated ClusterMessage comment

* Updated PluginSync to test against s3 + local storage

app/file.go

@@ -122,6 +122,19 @@ func (a *App) RemoveFile(path string) *model.AppError {
 	return backend.RemoveFile(path)
 }
 
+func (a *App) ListDirectory(path string) ([]string, *model.AppError) {
+	backend, err := a.FileBackend()
+	if err != nil {
+		return nil, err
+	}
+	paths, err := backend.ListDirectory(path)
+	if err != nil {
+		return nil, err
+	}
+
+	return *paths, nil
+}
+
 func (a *App) GetInfoForFilename(post *model.Post, teamId string, filename string) *model.FileInfo {
 	// Find the path from the Filename of the form /{channelId}/{userId}/{uid}/{nameWithExtension}
 	split := strings.SplitN(filename, "/", 5)