MM-41143: Pass a custom logger to morph (#19530)

We create a custom io.Writer to pass to the logger
instance. For now, we keep everything to debug
as all errors are surfaced back to the server via
the API.

```release-note
NONE
```

store/sqlstore/utils.go

@@ -147,3 +147,14 @@ func constructArrayArgs(ids []string) (string, []interface{}) {
 
 	return "(" + placeholder.String() + ")", values
 }
+
+// morphWriter is a target to pass to the logger instance of morph.
+// For now, everything is just logged at a debug level. If we need to log
+// errors/warnings from the library also, that needs to be seen later.
+type morphWriter struct {
+}
+
+func (l *morphWriter) Write(in []byte) (int, error) {
+	mlog.Debug(string(in))
+	return len(in), nil
+}