Add missing package-info

See gh-28047

spring-beans/src/main/java/org/springframework/beans/factory/generator/package-info.java

@@ -0,0 +1,9 @@
+/**
+ * Support for generating code that represents the state of a bean factory.
+ */
+@NonNullApi
+@NonNullFields
+package org.springframework.beans.factory.generator;
+
+import org.springframework.lang.NonNullApi;
+import org.springframework.lang.NonNullFields;