[Apigee X][API Product] Add support for optionsGroups

[mxr576]

This is available for a while but it is not supported by the PHP API client:
https://cloud.google.com/apigee/docs/reference/apis/apigee/rest/v1/organizations.apiproducts#operationgroup

Version: 2.0.15

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[mxr576]

@giteshk @phdhiren please re-open this issue, this is a still missing feature. Thank you