[MM-18150] plugin panic trace should not be lost (#13559)

* Transit panic from debug to error

* Parse plugin's StdErr and output panic to the mlog.Error

* Add unit tests

* Change log test

* Remove buffer from logger

* Remove 'panic' string filter

* Change *Buffer to io.Writer

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

mlog/log.go

@@ -144,6 +144,15 @@ func (l *Logger) StdLogWriter() io.Writer {
 	return &loggerWriter{f}
 }
 
+// StdErrPanicLogWriter returns a writer that can be hooked up to the output of a golang standard logger
+// all of the stderr will be interpreted as log entry.
+func (l *Logger) StdErrPanicLogWriter() io.Writer {
+	newLogger := *l
+	newLogger.zap = newLogger.zap.WithOptions(zap.AddCallerSkip(4), getStdLogOption())
+	f := newLogger.Error
+	return &panicLoggerWriter{f}
+}
+
 func (l *Logger) WithCallerSkip(skip int) *Logger {
 	newlogger := *l
 	newlogger.zap = newlogger.zap.WithOptions(zap.AddCallerSkip(skip))