Use terraform to automate GitHub access and permissions

Created by: jhchabran

Ported from @michaellzc suggestion on Slack

Pain-points:

• anyone can create a new repo on our own and become repo admin automatically, which bypass our policy
• hard to add individual team to repo (we by default only add the Teams -> Product & Engineering -> Engineering with write access to most repo), this makes tagging teams for PR review extremely hard)
• team repo membership is not really transparent.
• no way to self-serve access request but always relying on pinging the github-owners handle branch protection rule is no longer accessible due to lack of admin role to most teammates

Context at the time of creating this ticket:

@dcomas The problem is that we haven't had capacity from the owning teams to migrate to that right now.