New Check: Amazon ElastiCache Reserved Node Optimization

[brittandeyoung]

Summary

Checks your usage of ElastiCache and provides recommendations on purchase of Reserved Nodes.

Motivation

This allows us to recommend the number of each type of Reserved Node to purchase to maximize your savings.

Additional context

https://docs.aws.amazon.com/awssupport/latest/user/cost-optimization-checks.html#amazon-elasticache-reserved-node-optimization