Add RHEL Metering support to Cost Management flow for addon ELS for 1P

Given the low adoption rate, we agreed to redo tags.

New Tags

com_redhat_rhel_conversion=true/false (default false)
com_redhat_rhel_addon=els/future stuff (optional, can omit)
com_redhat_rhel=7/8/9 

This is a little more work than the original plan, but it's better to change now before we have wider adoption.

Previous design doc for tagging.
Current docs for tagging: https://access.redhat.com/documentation/en-us/cost_management_service/1-latest/html-single/managing_cost_data_using_tagging/index#adding-tags-to-an-AWS-resource_configuring-tags-int