Service user can use SDK release planner to plan for service or API version retirement

[josefree]

This is for both management plane and data plane. The scenarios required to support are

1. Service retirement leads to API and SDK retirement, and ultimately deprecation.
2. Service in public, but trying to retire some preview API versions, which leads to SDK retirement, and ultimately deprecation.
3. Service is retiring feature(s)/resource type(s), so they are retiring stable API versions with the feature(s) or resource types(s), which leads to SDK retirement, and ultimately deprecation.

Open question

1. When service consider to notify us the retirement
2. If service in different lifecycle stage can have different process of SDK retirement?
3. What's the process and stakkeholders of SDK publishing to retirement to deprecation?