Handle missing project configuration when the person who added a project left a team or a repository

Problem to solve

Currently, when the team member who added a project leaves a team or repository at GitLab:

1. We don't have a way reconfigure the project using a new token from another team member ❗
2. Users are still allowed to trigger prebuilds even if the webhook has been removed ❗

Could not reproduce the above for GitHub repositories as we'll need to set up the GitHub App.

Proposal

Following https://github.com/gitpod-io/gitpod/issues/7010, let's introduce a way to also reconfigure a project and re-installing a new webhook, etc.

This could be done using a new project settings area.

TBD (To be discussed)

Start by reading issue #7010 and reviewing the existing GitLab project-configuration and webhook flows. The scope is still to be discussed; done would mean a project settings area can reconfigure the project with another team member’s token, reinstall the webhook, and prevent prebuilds when the webhook is missing.