Indicate anti-wraparound autovacuum in log_autovacuum_min_duration

Hello
Currently log_autovacuum_min_duration log message has no difference between regular autovacuum and to prevent wraparound autovacuum. There are important differences, for example, backend can automatically cancel regular autovacuum, but not anti-wraparound. I think it is useful indicate anti-wraparound in logs.

Small patch attached. I am not sure can be anti-wraparound autovacuum not aggressive, so i leave all 4 variants.

regards, Sergei