[Plugin elasticache_info] includes the description of each replicatio…

…n group (ansible-collections#646)

[Plugin elasticache_info] includes the description of each replication group

SUMMARY
This pull request add the description of the corresponding Elasticache replication group into each described cache cluster.
ISSUE TYPE

Feature Pull Request

COMPONENT NAME
elasticache_info
ADDITIONAL INFORMATION
Actually the only way to describe Elasticache replication groups with Ansible is to use the dynamic inventory.
However, exposing the informations about each replication group could be useful in other contexts.
In my case, I am generating a few .env files and I need to include some Elasticache replication group primary endpoint and reader endpoint.
Since the elasticache_info plugin already exist and already retrieves the appropriate replication_group_id, I believe that this plugin should also retrieve the replication group description when it exists.
OTHER REMARKS CONCERNING THIS PULL REQUEST
Each provided description is copy/pasted from the official boto3 documentation which is distributed under an Apache 2.0 licence. I did it for consistency reason between and also because I am not a native speaker.
Also the provided description is incomplete : I only documented the fields that I was able to retrieve from my current AWS clusters.
Boto3 documentation of the "describe_replication_groups" function : https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/elasticache.html#ElastiCache.Client.describe_replication_groups
Moreover this pull request might violates the "integration tests" rule : I didn't find any integration test for the elasticache_info plugin and I don't know why no integration test have been made.

Reviewed-by: Mark Chappell <None>