Revise steward and editor roles

A 2022 a stewards team was created via #291. The list of stewards can be found here https://github.com/orgs/ipfs/teams/specs-stewards/members (although it's not publicly readable, as #367 points out.)

With a single, large set of stewards, it's unlikely that any steward is deeply familiar enough with the full surface area. In practice only 1-3 of these stewards have been actively engaged at any point in time. We should update to a core-and-area model, with a small number of core stewards responsible for keeping the spec family coherent and identifying the boundaries, and area editors (lightly inherited from IETF) responsible for specific areas.

Here are the 8 current areas, as defined in specs.ipfs.tech:
- Architecture
- Meta
- Routing
- Exchange
- HTTP Gateways
- Data Formats
- IPNS
- Content Filtering

Alternatively, we could have both "Area Directors" and individual "Spec Editors" (more closely mirroring IETF). But that may be too heavy — director seems like an inflated name for this context.

Start by reading the context in issues #291 and #367, then review the eight areas listed in specs.ipfs.tech. The work is done when the project has agreed on a core-and-area stewardship model, including the roles and responsibilities of core stewards and area editors, or a clearly justified alternative.

Written by the indexing model from the issue text.