Enhance the design proposal template with a graduation-criteria section

[EdDev]

The current design proposal template [1] is missing graduation criteria and feature lifecycle section. While suggesting an enhancement or change, it would be useful to put focus on the planning in regards to the feature graduation.

The subject has been discussed as part of the feature lifecycle proposal [2] and its relevance to the proposal template has been raised in this [3] thread.

[1] https://github.com/kubevirt/community/blob/main/design-proposals/proposal-template.md [3] https://github.com/kubevirt/community/pull/251/ [3] https://github.com/kubevirt/community/pull/251/files#r1489624264

Describe the solution you'd like:

It is suggested to update the design template with a new graduation criteria section that ref the feature-lifecycle and provides a plan for graduation.

Describe alternatives you've considered: N/A

[iholder101]

Thank you /cc

[fabiand]

@EdDev please see #288

As part of that proposal I'm suggesting to have an dedicated repo, with an issue per feature, and this issue is tracking the feature state until graduation. I'm suggesting a metadata file to track the graduation and deprecation more fine grained.