Add experimental support for cache-cleanup

- Includes basic implementation as `CacheCleaner`
- Integration test that checks unused files are removed:
  - Downloaded dependencies
  - Local build cache entries
  - Wrapper distributions

test/jest/resources/cache-cleanup/src/main/java/unused/dependencies/Library.java

@@ -0,0 +1,10 @@
+/*
+ * This Java source file was generated by the Gradle 'init' task.
+ */
+package unused.dependencies;
+
+public class Library {
+    public boolean someLibraryMethod() {
+        return true;
+    }
+}