Fix overflow on 32-bit systems when calculating idle time for eviction (#13804)

the `dictGetSignedIntegerVal` function should be used here,
because in some cases (especially on 32-bit systems) long may
be 4 bytes, and the ttl time saved in expires is a unix timestamp
(millisecond value), which is more than 4 bytes. In this case, we may
not be able to get the correct idle time, which may cause eviction
disorder, in other words, keys that should be evicted later may be
evicted earlier.

src/evict.c

@@ -162,7 +162,7 @@ int evictionPoolPopulate(redisDb *db, kvstore *samplekvs, struct evictionPoolEnt
             idle = 255-LFUDecrAndReturn(o);
         } else if (server.maxmemory_policy == MAXMEMORY_VOLATILE_TTL) {
             /* In this case the sooner the expire the better. */
-            idle = ULLONG_MAX - (long)dictGetVal(de);
+            idle = ULLONG_MAX - dictGetSignedIntegerVal(de);
         } else {
             serverPanic("Unknown eviction policy in evictionPoolPopulate()");
         }