Logger: only write subscribed topic format definitions

Previously the formats of all known uorb messages were written.

- reduces header size by about 13KB
- reduce ulog_message_format_s size to reduce required stack size.
  Largest message format is about 1000 bytes.

src/modules/logger/messages.h

@@ -67,7 +67,7 @@ struct ulog_message_format_s {
 	uint16_t msg_size; //size of message - ULOG_MSG_HEADER_LEN
 	uint8_t msg_type = static_cast<uint8_t>(ULogMessageType::FORMAT);
 
-	char format[2096];
+	char format[1500];
 };
 
 struct ulog_message_add_logged_s {