Don't log partial access log formats to INFO

[BrainStone]

Describe the bug Currently the AccessLogger plugin logs a line to info for every placeholder in the format string.
Now this isn't a huge deal, but fairly annoying regardless.

To Reproduce

1. Configure a web application with the AccessLogger plugin, for example like this:

   drogon::app().addPlugin("drogon::plugin::AccessLogger", {}, {});

2. Access any route
3. Notice the following log output

   20231029 01:19:29.756930 300331 INFO  $request_date $method $url [$body_bytes_received] ($remote_addr - $local_addr) $status $body_bytes_sent $processing_time - AccessLogger.cc:157
   20231029 01:19:29.757006 300331 INFO   $method $url [$body_bytes_received] ($remote_addr - $local_addr) $status $body_bytes_sent $processing_time - AccessLogger.cc:157
   20231029 01:19:29.757022 300331 INFO   $url [$body_bytes_received] ($remote_addr - $local_addr) $status $body_bytes_sent $processing_time - AccessLogger.cc:157
   20231029 01:19:29.757037 300331 INFO   [$body_bytes_received] ($remote_addr - $local_addr) $status $body_bytes_sent $processing_time - AccessLogger.cc:157
   20231029 01:19:29.757054 300331 INFO  ] ($remote_addr - $local_addr) $status $body_bytes_sent $processing_time - AccessLogger.cc:157
   20231029 01:19:29.757070 300331 INFO   - $local_addr) $status $body_bytes_sent $processing_time - AccessLogger.cc:157
   20231029 01:19:29.757085 300331 INFO  ) $status $body_bytes_sent $processing_time - AccessLogger.cc:157
   20231029 01:19:29.757100 300331 INFO   $body_bytes_sent $processing_time - AccessLogger.cc:157
   20231029 01:19:29.757115 300331 INFO   $processing_time - AccessLogger.cc:157

Source: https://github.com/drogonframework/drogon/blob/4323e7b6efc27326b779e239f7a95456ed689ea4/lib/src/AccessLogger.cc#L157

Expected behavior I would expect this log not exist, to be trace or at most debug level. Probably best to log the entire format as debug log and then the splitting can be done as trace.

[BrainStone]

That was quick! Thank you :)