impr(ci): use ghcr.io as the default container registry (#11210)

## Problem
Docker Hub has new rate limits coming up, and to avoid problems coming
with those we're switching to GHCR.

## Summary of changes
- Push images to GHCR initially and distribute them from there
- Use images from GHCR in docker-compose

.github/workflows/_check-codestyle-python.yml

@@ -15,11 +15,15 @@ defaults:
 jobs:
   check-codestyle-python:
     runs-on: [ self-hosted, small ]
+
+    permissions:
+      packages: read
+
     container:
       image: ${{ inputs.build-tools-image }}
       credentials:
-        username: ${{ secrets.NEON_DOCKERHUB_USERNAME }}
-        password: ${{ secrets.NEON_DOCKERHUB_PASSWORD }}
+        username: ${{ github.actor }}
+        password: ${{ secrets.GITHUB_TOKEN }}
       options: --init
 
     steps: