release: v0.6.0 — remove deprecated env var aliases (#704)

* chore: bump version to 0.6.0 and remove deprecated env var aliases

BREAKING CHANGES:
- POTATOMESH_INSTANCE removed — use INSTANCE_DOMAIN
- PROVIDER removed — use PROTOCOL
- MESH_SERIAL removed — use CONNECTION
- PORT config alias removed — use CONNECTION

The _ConfigModule proxy class (which kept PROTOCOL/PROVIDER and
CONNECTION/PORT in sync) is deleted. docker-compose.yml now defaults
INSTANCE_DOMAIN to http://web:41447 so deployments without an explicit
value continue to work.

* tests: run black

* address review comments

.github/workflows/docker.yml

@@ -188,7 +188,7 @@ jobs:
         docker pull ${{ env.REGISTRY }}/${{ env.IMAGE_PREFIX }}-ingestor-linux-amd64:${{ steps.version.outputs.version }}
         docker pull ${{ env.REGISTRY }}/${{ env.IMAGE_PREFIX }}-ingestor-linux-amd64:${{ steps.version.outputs.version_with_v }}
         docker run --rm --name ingestor-test \
-          -e POTATOMESH_INSTANCE=http://localhost:41447 \
+          -e INSTANCE_DOMAIN=http://localhost:41447 \
           -e API_TOKEN=test-token \
           -e CONNECTION=mock \
           -e DEBUG=1 \