Customized release plans workflows based on the scenario

**Issue:** The Release Planner App supports 3 workflows, new API Spec, new preview/stable API, Beta SDKs, & new stable API/stable SDKs. All of these workflows are tailored for Greenfield service scenario (no existing SDKs). There are additional tasks and requirements for the Greenfield scenario that are not required for the Brownfield scenario (existing SDKs).

**User feedback:** As of Feb 2024, all Brownfield services with existing generated SDKs can create and use release plans. However, the release plans have extra tasks and requirements which do not apply to these scenarios. Service partners have found the extra steps/requirements confusing, prompting them to reach out to the SDK team for help, which results in overall reduced productivity.

**Requirement:** The workflow should be tailored to the release scenario. Service partners should only see the steps/tasks/requirements that they are expected to complete for the API/SDK release in their release plan.

Scenarios:

Start by examining the Release Planner App's existing workflows and how release plans distinguish Greenfield from Brownfield services. Done means each release scenario shows only the steps, tasks, and requirements applicable to that API or SDK release, without the extra Greenfield requirements for Brownfield services.

Written by the indexing model from the issue text.