This switches from [`Teams.ListTeams`](https://pkg.go.dev/github.com/google/go-github/v41/github#TeamsService.ListTeams)
and potentially many calls of [`Teams.IsTeamRepoBySlug`](https://pkg.go.dev/github.com/google/go-github/v41/github#TeamsService.IsTeamRepoBySlug)
to just a single [`Repositories.ListTeams`](https://pkg.go.dev/github.com/google/go-github/v41/github#RepositoriesService.ListTeams),
which returns all the teams permissions to a specific repository.

This does have the minor drawback of not being able to distinguish
between teams not existing and teams not being in the organisation,
but this does also have the benefit of potentially speeding up the
result when there's many teams in the organisation.

For organizations with many members without write access (e.g. https://github.com/orgs/NixOS/people),
this speeds up the user check by switching from [`Organizations.ListMembers`](https://pkg.go.dev/github.com/google/go-github/v41/github#OrganizationsService.ListMembers)
to [`Repositories.ListCollaborators`](https://pkg.go.dev/github.com/google/go-github/v41/github#RepositoriesService.ListCollaborators).

Furthermore, using `ListCollaborators` we can easily check that the users
actually have write access to the repo, the same way as is done for
teams since the parent commit.