Remove samples (#22288)

Add code, that was used for documentation to the appropriate projects
or akka-docs.

akka-docs/rst/java/code/docs/cluster/FactorialResult.java

@@ -0,0 +1,15 @@
+package docs.cluster;
+
+import java.math.BigInteger;
+import java.io.Serializable;
+
+public class FactorialResult implements Serializable {
+	private static final long serialVersionUID = 1L;
+	public final int n;
+	public final BigInteger factorial;
+
+	FactorialResult(int n, BigInteger factorial) {
+		this.n = n;
+		this.factorial = factorial;
+	}
+}