Improve spec flow process

[oskarth]

This issue is basically about cleaning up the process for Status specs similarly to what has been done for Vac specs*.

Problem

Currently we use the COSS model (https://github.com/unprotocols/rfc/blob/master/2/README.md) for change management.

However, we don't do so fully and have some ad hoc processes. This complicates things needlessly, around versioning, breaking urls, etc.

Proposed solution

Implement it more fully and document that this is the case.

Notes

Specific things that stand out to me:

1. Lack of editor/contributor distinction
2. A bit too much ceremony for draft changes
3. Random non cosmetic changes to stable
4. Lack of canonical URLs leading to breaking urls
5. Not retiring unused specs
6. General ad hoc flow documented in a bunch of different places

Also see https://github.com/vacp2p/specs/issues/234

See how it works for Vac RFCs here https://rfc.vac.dev/ and the required changes vacp2p/rfc#235
See vacp2p/rfc#235