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

plugin/.stutter/java11.lock

@@ -5,4 +5,6 @@
 5.3.1
 5.4.1
 5.5.1
-5.6.3
+5.6.4
+6.0.1
+6.1

plugin/.stutter/java8.lock

@@ -12,4 +12,6 @@
 5.3.1
 5.4.1
 5.5.1
-5.6.3
+5.6.4
+6.0.1
+6.1