Redis 6 compatibility

[iddm]

Even though the crate has the corresponding features to support various Redis server versions, varying from Redis 6 to the very latest Redis 7.2, the tests actually fail when running with Redis 6.

For example, running make test with Redis 6 leads to:

*** FATAL CONFIG FILE ERROR (Redis 6.0.16) ***
Reading the configuration file, at line 4
>>> 'enable-debug-command "yes"'
Bad directive or wrong number of arguments

The tests need to be runnable against Redis 6, and the CI workflows need to be added.

[iddm]

My branch where I fixed some issues: https://github.com/RedisLabsModules/redismodule-rs/tree/fix-redis-6-tests