Remove bcopy(), bzero(), bcmp()

bcopy() has a confusing argument order and is actually a move, not a
copy; they're all deprecated since POSIX.1-2001 and removed in -2008,
and we shim them out to mem*() on Linux anyway

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #12996

cmd/raidz_test/raidz_bench.c

@@ -63,7 +63,7 @@ bench_fini_raidz_maps(void)
 {
 	/* tear down golden zio */
 	raidz_free(zio_bench.io_abd, max_data_size);
-	bzero(&zio_bench, sizeof (zio_t));
+	memset(&zio_bench, 0, sizeof (zio_t));
 }
 
 static inline void