Document more services and permissions of the cargo team

[ehuss]

This updates the contributor guide with more information about what services and permissions are available to the Cargo team. This is primarily to capture that we have a new rust-lang/cargo-team repository. I took the opportunity to update some related information.

[rustbot]

r? @epage

rustbot has assigned @epage.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[epage]

---- bad_config::github_pull_request_url stdout ----
running `/home/runner/work/cargo/cargo/target/debug/cargo check -v`

thread 'bad_config::github_pull_request_url' (114161) panicked at tests/testsuite/bad_config.rs:2351:10:

test failed running `/home/runner/work/cargo/cargo/target/debug/cargo check -v`
error: process exited with code -1 (expected 101)
--- stdout

--- stderr
    Updating git repository `[https://github.com/rust-lang/does-not-exist/pull/123`](https://github.com/rust-lang/does-not-exist/pull/123%60)
error: failed to get `bar` as a dependency of package `foo v0.0.0 (/home/runner/work/cargo/cargo/target/tmp/cit/t5/foo)`

Caused by:
  failed to load source for dependency `bar`

Caused by:
  Unable to update https://github.com/rust-lang/does-not-exist/pull/123

Caused by:
  failed to clone into: /home/runner/work/cargo/cargo/target/tmp/cit/t5/home/.cargo/git/db/123-5f7431990887bb14

Caused by:
  network failure seems to have happened
  if a proxy or similar is necessary `net.git-fetch-with-cli` may help here
  https://doc.rust-lang.org/cargo/reference/config.html#netgit-fetch-with-cli

  note: GitHub url https://github.com/rust-lang/does-not-exist/pull/123 is not a repository. 
  help: Replace the dependency with 
         `git = "https://github.com/rust-lang/does-not-exist.git" rev = "refs/pull/123/head"` 
     to specify pull requests as dependencies' revision.

Caused by:
  An IO error occurred when talking to the server

Caused by:
  Received HTTP status 404

note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace