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-context/src/main/java/org/springframework/instrument/classloading/glassfish/package-info.java

@@ -1,4 +1,7 @@
 /**
  * Support for class instrumentation on GlassFish.
  */
+@NullUnmarked
 package org.springframework.instrument.classloading.glassfish;
+
+import org.jspecify.annotations.NullUnmarked;

spring-context/src/main/java/org/springframework/instrument/classloading/jboss/package-info.java

@@ -1,4 +1,7 @@
 /**
  * Support for class instrumentation on JBoss AS 6 and 7.
  */
+@NullUnmarked
 package org.springframework.instrument.classloading.jboss;
+
+import org.jspecify.annotations.NullUnmarked;

spring-context/src/main/java/org/springframework/instrument/classloading/package-info.java

@@ -2,4 +2,7 @@
  * Support package for load time weaving based on class loaders,
  * as required by JPA providers (but not JPA-specific).
  */
+@NullUnmarked
 package org.springframework.instrument.classloading;
+
+import org.jspecify.annotations.NullUnmarked;

spring-context/src/main/java/org/springframework/instrument/classloading/tomcat/package-info.java

@@ -1,4 +1,7 @@
 /**
  * Support for class instrumentation on Tomcat.
  */
+@NullUnmarked
 package org.springframework.instrument.classloading.tomcat;
+
+import org.jspecify.annotations.NullUnmarked;