Set HIDDEN_CONFIG flag on events-per-io-thread (valkey-io#1408)

events-per-io-thread is for testing purposes that allow us to force the
main thread to always offload the works to the IO threads, see
adjustIOThreadsByEventLoad for more details.

Signed-off-by: Binbin <[email protected]>

src/config.c

@@ -3271,7 +3271,7 @@ standardConfig static_configs[] = {
     createIntConfig("databases", NULL, IMMUTABLE_CONFIG, 1, INT_MAX, server.dbnum, 16, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("port", NULL, MODIFIABLE_CONFIG, 0, 65535, server.port, 6379, INTEGER_CONFIG, NULL, updatePort),                                   /* TCP port. */
     createIntConfig("io-threads", NULL, DEBUG_CONFIG | IMMUTABLE_CONFIG, 1, IO_THREADS_MAX_NUM, server.io_threads_num, 1, INTEGER_CONFIG, NULL, NULL), /* Single threaded by default */
-    createIntConfig("events-per-io-thread", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, server.events_per_io_thread, 2, INTEGER_CONFIG, NULL, NULL),
+    createIntConfig("events-per-io-thread", NULL, MODIFIABLE_CONFIG | HIDDEN_CONFIG, 0, INT_MAX, server.events_per_io_thread, 2, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("prefetch-batch-max-size", NULL, MODIFIABLE_CONFIG, 0, 128, server.prefetch_batch_max_size, 16, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("auto-aof-rewrite-percentage", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, server.aof_rewrite_perc, 100, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("cluster-replica-validity-factor", "cluster-slave-validity-factor", MODIFIABLE_CONFIG, 0, INT_MAX, server.cluster_replica_validity_factor, 10, INTEGER_CONFIG, NULL, NULL), /* replica max data age factor. */