Parallelize council work with dismissal

[jyasskin]

Right now, https://www.w3.org/policies/process/drafts/#council-participation says

Before a Council forms, the Team presents the entire list of potential members and collected reasons and responses to the potential Council members, who then consider for each potential member whether that individual’s participation would compromise the integrity of the Council decision, and vote whether to dismiss that potential member.

In the case of the Vibration council, this led to:

1. A Team decision that a council was needed, at latest on 2025-03-12.
2. Collecting dismissal reasons from the AC, from 2025-03-12 to 2025-03-28.
3. A delay from 2025-03-28 to 2025-04-30, while the Team set up the dismissal poll for potential council members.
4. A dismissal poll from 2025-04-30 to 2025-05-14.

Adding up to a council that will start at least 2 months after it was clear that a council was needed. Even with no delay in starting the dismissal poll, this is still a minimum of 1 month where the council can't start on its work.

Instead, councils should be able to start their work in parallel with the dismissal process.

A council could do many things while it's waiting to see who will be dismissed. It could pick a chair by consensus, but not by vote. It could attempt to broker consensus, gather members' initial impressions, research the disagreement, and draft an initial report. It should not be able to resort to voting or issue its final report.

If any members want certain other members dismissed and are uncomfortable discussing the topic until that happens, they need to be able to delay the process until dismissal is finished. They could do this by withholding consensus on the chair selection, by talking to the selected chair about their concerns, or in extreme cases, by waiting to comment until the time between when dismissal finishes and the final report is issued.

Renunciation should be able to happen instantaneously.

Thanks to @martinthomson for the core of this idea.