putMetric to support addition of custom metrics in CloudWatch

I have a use case where I want to enable high resolution metrics in CloudWatch. This is done via setting the 'StorageResolution' parameter in put-metric-data API to a value from 1 to 60. Currently putMetric only has these parameters (metricName, value, unit) and support for publishing custom metrics is missing.

Links - [Publishing Custom Metrics](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/publishingMetrics.html), [put-metric-data api ](https://docs.aws.amazon.com/cli/latest/reference/cloudwatch/put-metric-data.html)

Start at the putMetric entry point and compare its current metricName, value, and unit parameters with the linked CloudWatch put-metric-data API documentation. Determine how custom metrics and the StorageResolution value from 1 to 60 should be represented, then verify that the resulting metrics can be published through the existing client flow.

Written by the indexing model from the issue text.