Add test for aggregation issue (#9046)

Author: nickdrozd

tests/pyreverse/functional/class_diagrams/aggregation/fields.mmd

@@ -0,0 +1,24 @@
+classDiagram
+  class A {
+    x
+  }
+  class B {
+    x
+  }
+  class C {
+    x
+  }
+  class D {
+    x
+  }
+  class E {
+    x
+  }
+  class P {
+  }
+  P --* A : x
+  P --* C : x
+  P --* D : x
+  P --* E : x
+  P --o B : x
+  P --o C : x

tests/pyreverse/functional/class_diagrams/aggregation/fields.py

@@ -0,0 +1,27 @@
+# Test for https://github.com/pylint-dev/pylint/issues/9045
+
+class P:
+    pass
+
+class A:
+    x: P
+
+class B:
+    def __init__(self, x: P):
+        self.x = x
+
+class C:
+    x: P
+
+    def __init__(self, x: P):
+        self.x = x
+
+class D:
+    x: P
+
+    def __init__(self):
+        self.x = P()
+
+class E:
+    def __init__(self):
+        self.x = P()