Use sync_id instead of use_banner while building statsd metric messages

This writes fuzzer_stats to a temp file and then atomically renames the
temp file into fuzzer_stats so that any read on fuzzer_stats will always
return a consistent view of the AFL state (otherwise there is a very
low change of AFL's write and $tool's reads to race and yield
inconsistent results).

Make fuzzer_stats update atomic

Use EarlyEPCallback when llvm >= 16

2 typos in afl-llvm-pass.so.cc

Use proper AFL_NYX_AUX_SIZE for nyx_aux_string