[8.x] Fix possible out of memory error when deleting values by reference key from cache in Redis driver

[dkuzmenchuk]

This PR solves possible out of memory issue when deleting values by reference key from cache in Redis driver. PR contains changes from #39939, but also takes into consideration that Laravel supports 2 Redis clients: phpredis and predis (issue #40037).

Changes from the PR #39939:

1. In case of empty results of sscan command predis client returns default cursor value and empty array. At the same time phpredis just returns false.
   To process this I suggest break the loop if $valuesChunk is null. Because array destruction on false writes null to all array items.

2. phpredis returns integer values as cursor. So we should cast $cursor to string to make a correct comparison with a default value.

3. Options for sscan command are in lowercase to work correct with both Redis clients. Otherwise phpredis processes set by 10 items per iteration