Move Cilium Org Team Review Notification Automation to Cilium Community Repository

[jspaleta]

Cilium Project currently relies on some team review notification management automation that resides in a private Isovalent org repository. Let's fix that!

I've put a plan together to transition the github action and team management configuration for the cilium org into the community repository, please take a look and make suggestions in that document.

This transition does require some coordination with org/repo admins, I cover the details of the coordinated actions in step 1 in the plan document.

ref: Cilium Team Review Notification Automation Plan Google Doc for comments

Initial planned mergable changes to the Cilium community repo:

1. add team-management subdirectory to hold cilium-team-assignments.yaml configuration file
2. add github team-manager workflow automation that will update review notification exclusions on main branch merge

I'm going to stub out a draft PR with these changes. The necessary workflow job environment secret I believe requires org/repo admin level access to generate. I'll breadcrumb some comments in the workflow in the draft PR pointing to the needed prereq environment secret.