Extract platform manifests to a separate repository

[arikkfir]

So final structure would be:

delivery
   |
   +--- clusters
   |       |
   |       +--- <cluster name>
   |              |
   |              +--- <cluster contents>
   |
   +--- environments
   |       |
   |       +--- <environment name>
   |              |
   |              +--- <environment contents>
   |
   +--- etc
           |
           +--- misc configurations

<app repository>
   |
   +--- .github/workflows
   |       |
   |       +--- main_deploy.yaml   # <- deploys "main" to the main (production) environment
   |       +--- pr_deploy.yaml     # <- deploys PRs to their respective environment
   |       +--- pr_undeploy.yaml   # <- undeploys PRs from their respective environment
   |       +--- push.yaml          # <- builds each push
   |
   +--- deploy
   |       |
   |       +--- <deployment manifests>
   |
   +--- <other content>