Add environments to group and project ci_access config

We need a way for users to restrict CI access to Kubernetes agents to selected environments. This can be done by adding environments in the groups and projects ci_access in the agent config saved in a project's repository.

This change allows the GitLab Agent Server to read the environments configuration and push that back to the GitLab instance to be persisted in the database through the POST /internal/kubernetes/agent_configuration API

Issue: gitlab-org/gitlab#343885 (closed)

Screenshots

Agent config.yaml in repository

Configurations persisted to the GitLab database through the POST /internal/kubernetes/agent_configuration API