Figure out automation of the "all" team on GH

[jamesmunns]

We have a team, "all", that is not managed by the rust-lang teams bots.

All other teams have a toml that has a section like this:

[[github]]
orgs = ["rust-embedded"]
team-name = "resources"

If we want the bot to manage the team access for the "all" account, I think we either need to:

• add a wg-embedded-all.toml manifest to the rust-lang-team/teams folder: https://github.com/rust-lang/team/tree/master/teams
• Add the [[github]] metadata to the wg-embedded.toml manifest, treating it as the source for the "all" team.
• Get rid of the all team, as it's manually maintained atm

CC @therealprof, who I THINK set this all up originally. I'm not familiar enough with teams automation to know which option is right, but this came up with thejpster retiring.

[BartMassey]

Option 4: Construct the all team as the union of the team manifests in CI. Optionally check to ensure that this matches the [[github]] manifest.

Or is the [[github]] manifest already this?

[jamesmunns]

@BartMassey looking at the toml docs: https://github.com/rust-lang/team/blob/master/docs/toml-schema.md

It appears we could instead:

• remove all people.members of wg-embeded.toml
• add a people.included-teams section, listing all substeams
• add the [[github]] section as proposed above

[jamesmunns]

We should also add website.zulip-stream while we are at it.