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/dependency/snapshot/groovy/build.gradle

@@ -0,0 +1,12 @@
+plugins {
+    id "java"
+}
+
+repositories {
+    mavenCentral()
+    maven { url "https://oss.sonatype.org/content/repositories/snapshots/" }
+}
+
+dependencies {
+    implementation "com.squareup.okio:okio:2.5.0-SNAPSHOT"
+}