logger: add NewStdLogger that can be used as std *log.Logger

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

logger/stdlogger.go

@@ -0,0 +1,19 @@
+package logger
+
+import (
+	"log"
+)
+
+type stdLogger struct {
+	l     Logger
+	level Level
+}
+
+func NewStdLogger(l Logger, level Level) *log.Logger {
+	return log.New(&stdLogger{l: l, level: level}, "" /* prefix */, 0 /* flags */)
+}
+
+func (sl *stdLogger) Write(p []byte) (int, error) {
+	sl.l.Log(sl.l.Options().Context, sl.level, string(p))
+	return len(p), nil
+}