Use custom dependency resolution

- Use Apache Ivy to resolve artifact URLs
- Update build model with full artifact IDs
- Generate Maven module metadata to support dynamic version constraints
- Resolve snapshot versions and generate snapshot metadata
- Add test fixtures and rewrite Gradle plugin tests
- Update dependencies

fixtures/subprojects/dependent-subprojects/groovy/settings.gradle

@@ -0,0 +1 @@
+include ':child-a', ':child-b', ':child-c', ':child-d'