feat: add plain-HTTP listeners for various repository configurations to support non-HTTPS access

Signed-off-by: d9pouces <github@19pouces.net>

tests/configs/Java.yaml.j2

@@ -23,7 +23,8 @@ configurations:
     # during the Dockerfile's warm-up step. All other tools just see it as
     # an ordinary repository, and find the test artifact here.
     - name: central
-      url: https://host.docker.internal:{{ 'JAVA_REPO_PORT' | env }}/
+{% set scheme = 'JAVA_REPO_SCHEME' | env %}
+      url: {{ scheme }}://host.docker.internal:{{ ('JAVA_REPO_PORT' if scheme == 'https' else 'JAVA_REPO_HTTP_PORT') | env }}/
     # Second entry: only SBT needs this. With
     # -Dsbt.override.build.repos=true (the only way SBT actually consults
     # this file for project dependencies, not just its own bootstrap), the