lib/config: Decouple VerifyConfiguration from Committer (#7939)

... and remove 8/10 implementations, which were no-ops. This saves code
and time copying configurations.

lib/model/model.go

@@ -168,6 +168,8 @@ type model struct {
 	foldersRunning int32
 }
 
+var _ config.Verifier = &model{}
+
 type folderFactory func(*model, *db.FileSet, *ignore.Matcher, config.FolderConfiguration, versioner.Versioner, events.Logger, *util.Semaphore) service
 
 var (

lib/model/progressemitter.go

@@ -212,11 +212,6 @@ func (t *ProgressEmitter) computeProgressUpdates() []progressUpdate {
 	return progressUpdates
 }
 
-// VerifyConfiguration implements the config.Committer interface
-func (t *ProgressEmitter) VerifyConfiguration(from, to config.Configuration) error {
-	return nil
-}
-
 // CommitConfiguration implements the config.Committer interface
 func (t *ProgressEmitter) CommitConfiguration(_, to config.Configuration) bool {
 	t.mut.Lock()