Breaking Change PR checks should flag changes in tags

Some consumers of the REST API definitions in this repo use tags on operations for grouping or other purposes, and changes in tag names can cause disruption / breaking changes in the artifacts they produce. An example is the Terraform generators that produce the Terraform plugin for Azure based on the REST API definition.

To avoid breaking changes in these down-stream consumers, we should avoid changes to tag names except where necessary, and we should enhance the Breaking Changes PR checks (openapi-diff) to flag changes to tag names.