ResourceType metric dimension differs from java and python plugin

The [java](https://github.com/aws-cloudformation/cloudformation-cli-java-plugin/blob/4bdae6ec8d27543fa0ca9a4d50515cdf325ad953/src/main/java/software/amazon/cloudformation/metrics/MetricsPublisherImpl.java#L42) and [python](https://github.com/aws-cloudformation/cloudformation-cli-python-plugin/blob/master/src/cloudformation_cli_python_lib/metrics.py#L40) plugins report `ResourceType` metric dimension as `AWS::Org::Name` and the [go plugin](https://github.com/aws-cloudformation/cloudformation-cli-go-plugin/blob/master/cfn/metrics/publisher.go#L48) reports `AWS/Org/Name`. Users should expect each cloudformation resource provider plugin to report metrics in the same way.

I'm filling this issue to start a discussion on how this should be fixed forward. While it's a simple code change, it's a backwards incompatible change for users that are relying on the current metric format.

The Go implementation is linked at cfn/metrics/publisher.go around line 48; compare its ResourceType dimension with the linked Java and Python implementations. First investigate the backwards-compatibility implications of changing AWS/Org/Name to AWS::Org::Name, then verify the chosen metric format and its effect on existing users.

Written by the indexing model from the issue text.