chore: update GitHub automation for IAM team

Created by: unknwon

Three parts of GitHub automation have been updated for the IAM team:

1. .github/teams.yml: Automatically label the PR with the label team/iam if the author is one of the defined people.
   • Also only limited to pull requests "opened" and "reopened" events, give us a chance to transfer PR ownership or not intended to be going to the team board.
2. .github/workflows/label-move.yml: Automatically add issues and PRs with the label team/iam to the IAM GitHub project.
3. .github/workflows/label-notify.yml: Automatically tag @sourcegraph/iam team when an issue is labeled with team/iam

Test plan

Not code related.