Add a test suite to the team repository

[pietroalbini]

Up until now there was no test suite for the team repository, and that started to bite us recently (for example with the inclusion of working group leads in the leads team).

This PR adds a test suite to the team repository similar to compiletest: inside tests/static-api there is another "team repository" with some dummy data, and the test suite ensures its output of the static API matches the expected one committed to the repository. If the output doesn't match a diff is displayed, and the tests/bless.sh script can be used to bless the new output.

The test suite doesn't fully cover everything yet, but it's a start: I'll followup with other PRs in the near future.

[Mark-Simulacrum]

I think I would prefer to use dummy (e.g., bot -- including existing) accounts for the testing. While I don't plan to leave anytime soon, I do semi-frequently run things like rg <username> in the team repo to find out what teams a user is on, and having users belong to test-only teams seems annoying for that.

[pietroalbini]

@Mark-Simulacrum good point!

I changed all the users in tests with dummy users, and added a --skip flag to cargo run check to skip individual validation checks (since we need to disable the validate_github_usernames check).

[Mark-Simulacrum]

This looks good to me with CI fixed.