all: Get rid of fatal logging (#5537)

* cleanup Fatal in lib/config/config.go

* cleanup Fatal in lib/config/folderconfiguration.go

* cleanup Fatal in lib/model/model.go

* cleanup Fatal in cmd/syncthing/monitor.go

* cleanup Fatal in cmd/syncthing/main.go

* cleanup Fatal in lib/api

* remove Fatal methods from logger

* lowercase in errors.Wrap

* one less channel

cmd/syncthing/monitor.go

@@ -85,18 +85,18 @@ func monitorMain(runtimeOptions RuntimeOptions) {
 
 		stderr, err := cmd.StderrPipe()
 		if err != nil {
-			l.Fatalln("stderr:", err)
+			panic(err)
 		}
 
 		stdout, err := cmd.StdoutPipe()
 		if err != nil {
-			l.Fatalln("stdout:", err)
+			panic(err)
 		}
 
 		l.Infoln("Starting syncthing")
 		err = cmd.Start()
 		if err != nil {
-			l.Fatalln(err)
+			panic(err)
 		}
 
 		stdoutMut.Lock()