[Feature][Add] Secrets generation by the Operator

[shubham-cmyk]

fix #269

Secrets now can be generate by the operator.
Package added : https://github.com/google/uuid // for the Password generation.

Expected Working :
User can either create the secret itself or offload the generation to the operator.
Operator Create the Secret using the given name and namespace;
If namespace is empty the namespace of the redis setup is taken by the operator.
if no key is passed the default key is "key"

[darkrift]

Any reason not to leverage https://redis.io/commands/acl-genpass/ ?

[shubham-cmyk]

This could be used that's why this PR was on hold for so long

[shubham-cmyk]

@darkrift I would like you to invite to slack channel : Join our #redis-operator Slack Channel.