Add compatibility tests for initializing Attribute with Rule/StatefuleRule and initial value

Author: jcmosc

Tests/OpenAttributeGraphCompatibilityTests/Attribute/Attribute/AttributeCompatibilityTests.swift

@@ -14,6 +14,37 @@ struct AttributeCompatibilityTests {
         #expect(intAttribute.value == 0)
     }
 
+    @Test
+    func initWithRule() {
+        struct TestRule: Rule {
+            var value: Int {
+                return 0
+            }
+        }
+        let attribute1 = Attribute(TestRule())
+        #expect(attribute1.value == 0)
+        
+        let attribute2 = Attribute(TestRule(), initialValue: 1)
+        #expect(attribute2.value == 1)
+    }
+    
+    @Test
+    func initWithStatefulRule() {
+        struct TestStatefuleRule: StatefulRule {
+            typealias Value = Int
+            func updateValue() {
+                withUnsafePointer(to: 0) { ptr in
+                    Graph.setOutputValue(ptr)
+                }
+            }
+        }
+        let attribute1 = Attribute(TestStatefuleRule())
+        #expect(attribute1.value == 0)
+        
+        let attribute2 = Attribute(TestStatefuleRule(), initialValue: 1)
+        #expect(attribute2.value == 1)
+    }
+    
     @Test
     func hashableAndEquatable() {
         let a = Attribute<Int>(identifier: .nil)