change default packagemanifests/bundle channel accordingly with the channel naming conventions

Feature Request

Describe the problem you need a feature to resolve.

SDK and OLM are projects from the same organization and one of our goals is to make them aligned and closer as much as possible. Therefore, keeping a consensus across the board makes it easier for the users to understand. However, besides the recommendation to create fast/candidate/stable as channel names, we are scaffolding alpha. See; https://olm.operatorframework.io/docs/best-practices/channel-naming/#naming

Our motivation with this convention is to encourage a better user experience for OLM users to have an intuitively
understanding of the level of maturity and supportability of the solutions that will get installed. It can get very complex
for cluster admins and Operator consumers in general when each solution distributes in the OLM catalogue adopt different names or different meanings for the same terminologies.

Note that many authors publish their solutions with what is scaffold by default and it has been ended up with many projects using alpha channel. (not desired)

Describe the solution you'd like.

Use a channel naming according to the recommendations instead of alpha. (It is required to discuss and confirm what should the default value, however, so far that seems that could be candidate )

Review the linked OLM channel-naming recommendation and the SDK's default packagemanifests/bundle scaffolding. Confirm the replacement for alpha with maintainers; the issue suggests candidate but leaves the default unresolved. Once agreed, update the relevant default and verify that newly scaffolded projects use the selected channel name.