Extracted transport part of the code into separate file. All code dealing with serializing/deserializing is moved int srv/event/ngx_event_quic_transport.c/h file. All macros for dealing with data are internal to source file. The header file exposes frame types and error codes. The exported functions are currently packet header parsers and writers and frames parser/writer. The ngx_quic_header_t structure is updated with 'log' member. This avoids passing extra argument to parsing functions that need to report errors.