Cleaned up hexdumps in debug output. - the ngx_quic_hexdump0() macro is renamed to ngx_quic_hexdump(); the original ngx_quic_hexdump() macro with variable argument is removed, extra information is logged normally, with ngx_log_debug() - all labels in hex dumps are prefixed with "quic" - the hexdump format is simplified, length is moved forward to avoid situations when the dump is truncated, and length is not shown - ngx_quic_flush_flight() function contents is debug-only, placed under NGX_DEBUG macro to avoid "unused variable" warnings from compiler - frame names in labels are capitalized, similar to other places