Add support for setting and getting ttl (milliseconds) of redis cache key
Entitlements V2 requires support for setting and getting the ttl of redis cache keys. The new advanced cache implementation in Entitlements V2 will flush the cache entries on write operations by setting the ttl to a given low-high range (less than 1 min). In the case of multiple write operations occurring within the flush ttl time range and impacting the same key, we want to check the current ttl of that key so that if the current ttl is lower than the flush ttl, we let that cache entry timeout instead of resetting its ttl.