Upgrade to nullability plugin 0.0.9

This commit also replaces Arch Unit packageInfoShouldBeNullMarked() rule
by either configuring requireExplicitNullMarking = false when the whole
module does not have JSpecify annotations, or explicit @NullUnmarked
when some have and some don't.

See gh-36054

spring-core/src/main/java/org/springframework/aot/nativex/feature/package-info.java

@@ -1,4 +1,7 @@
 /**
  * GraalVM native image features, not part of Spring Framework public API.
  */
+@NullUnmarked
 package org.springframework.aot.nativex.feature;
+
+import org.jspecify.annotations.NullUnmarked;

spring-core/src/main/java/org/springframework/aot/nativex/substitution/package-info.java

@@ -1,4 +1,7 @@
 /**
  * GraalVM native image substitutions, not part of Spring Framework public API.
  */
+@NullUnmarked
 package org.springframework.aot.nativex.substitution;
+
+import org.jspecify.annotations.NullUnmarked;

spring-core/src/main/java/org/springframework/asm/package-info.java

@@ -10,4 +10,7 @@
  * <p>As this repackaging happens at the class file level, sources
  * and javadocs are not available here.
  */
+@NullUnmarked
 package org.springframework.asm;
+
+import org.jspecify.annotations.NullUnmarked;

spring-core/src/main/java/org/springframework/cglib/beans/package-info.java

@@ -3,4 +3,7 @@
  * <a href="https://github.com/cglib/cglib">CGLIB</a> beans package
  * (for internal use only).
  */
+@NullUnmarked
 package org.springframework.cglib.beans;
+
+import org.jspecify.annotations.NullUnmarked;

spring-core/src/main/java/org/springframework/cglib/core/internal/package-info.java

@@ -3,4 +3,7 @@
  * <a href="https://github.com/cglib/cglib">CGLIB</a> core internal package
  * (for internal use only).
  */
+@NullUnmarked
 package org.springframework.cglib.core.internal;
+
+import org.jspecify.annotations.NullUnmarked;

spring-core/src/main/java/org/springframework/cglib/core/package-info.java

@@ -3,4 +3,7 @@
  * <a href="https://github.com/cglib/cglib">CGLIB</a> core package
  * (for internal use only).
  */
+@NullUnmarked
 package org.springframework.cglib.core;
+
+import org.jspecify.annotations.NullUnmarked;

spring-core/src/main/java/org/springframework/cglib/package-info.java

@@ -7,4 +7,7 @@
  * dependencies on CGLIB at the application level or from third-party
  * libraries and frameworks.
  */
+@NullUnmarked
 package org.springframework.cglib;
+
+import org.jspecify.annotations.NullUnmarked;

spring-core/src/main/java/org/springframework/cglib/proxy/package-info.java

@@ -3,4 +3,7 @@
  * <a href="https://github.com/cglib/cglib">CGLIB</a> proxy package
  * (for internal use only).
  */
+@NullUnmarked
 package org.springframework.cglib.proxy;
+
+import org.jspecify.annotations.NullUnmarked;

spring-core/src/main/java/org/springframework/cglib/reflect/package-info.java

@@ -3,4 +3,7 @@
  * <a href="https://github.com/cglib/cglib">CGLIB</a> reflect package
  * (for internal use only).
  */
+@NullUnmarked
 package org.springframework.cglib.reflect;
+
+import org.jspecify.annotations.NullUnmarked;

spring-core/src/main/java/org/springframework/cglib/transform/impl/package-info.java

@@ -3,4 +3,7 @@
  * <a href="https://github.com/cglib/cglib">CGLIB</a> transform impl package
  * (for internal use only).
  */
+@NullUnmarked
 package org.springframework.cglib.transform.impl;
+
+import org.jspecify.annotations.NullUnmarked;

spring-core/src/main/java/org/springframework/cglib/transform/package-info.java

@@ -3,4 +3,7 @@
  * <a href="https://github.com/cglib/cglib">CGLIB</a> transform package
  * (for internal use only).
  */
+@NullUnmarked
 package org.springframework.cglib.transform;
+
+import org.jspecify.annotations.NullUnmarked;

spring-core/src/main/java/org/springframework/cglib/util/package-info.java

@@ -3,4 +3,7 @@
  * <a href="https://github.com/cglib/cglib">CGLIB</a> util package
  * (for internal use only).
  */
+@NullUnmarked
 package org.springframework.cglib.util;
+
+import org.jspecify.annotations.NullUnmarked;

spring-core/src/main/java/org/springframework/objenesis/package-info.java

@@ -12,4 +12,7 @@
  * <a href="http://objenesis.org/tutorial.html">Objenesis docs</a>
  * for details when working with these classes.
  */
+@NullUnmarked
 package org.springframework.objenesis;
+
+import org.jspecify.annotations.NullUnmarked;