Make inner classes static where possible

Closes gh-22804

spring-aop/src/main/java/org/springframework/aop/aspectj/annotation/InstantiationModelAwarePointcutAdvisorImpl.java

@@ -263,7 +263,7 @@ final class InstantiationModelAwarePointcutAdvisorImpl
 	 * Note that this is a <i>dynamic</i> pointcut; otherwise it might be optimized out
 	 * if it does not at first match statically.
 	 */
-	private final class PerTargetInstantiationModelPointcut extends DynamicMethodMatcherPointcut {
+	private static final class PerTargetInstantiationModelPointcut extends DynamicMethodMatcherPointcut {
 
 		private final AspectJExpressionPointcut declaredPointcut;
 

spring-context/src/main/java/org/springframework/context/annotation/CommonAnnotationBeanPostProcessor.java

@@ -565,7 +565,7 @@ public class CommonAnnotationBeanPostProcessor extends InitDestroyAnnotationBean
 	 * Class representing generic injection information about an annotated field
 	 * or setter method, supporting @Resource and related annotations.
 	 */
-	protected abstract class LookupElement extends InjectionMetadata.InjectedElement {
+	protected abstract static class LookupElement extends InjectionMetadata.InjectedElement {
 
 		protected String name = "";
 

spring-core/src/main/java/org/springframework/core/convert/support/IntegerToEnumConverterFactory.java

@@ -35,7 +35,7 @@ final class IntegerToEnumConverterFactory implements ConverterFactory<Integer, E
 	}
 
 
-	private class IntegerToEnum<T extends Enum> implements Converter<Integer, T> {
+	private static class IntegerToEnum<T extends Enum> implements Converter<Integer, T> {
 
 		private final Class<T> enumType;
 

spring-core/src/main/java/org/springframework/core/convert/support/StringToEnumConverterFactory.java

@@ -35,7 +35,7 @@ final class StringToEnumConverterFactory implements ConverterFactory<String, Enu
 	}
 
 
-	private class StringToEnum<T extends Enum> implements Converter<String, T> {
+	private static class StringToEnum<T extends Enum> implements Converter<String, T> {
 
 		private final Class<T> enumType;
 

spring-tx/src/main/java/org/springframework/transaction/interceptor/TransactionAspectSupport.java

@@ -617,7 +617,7 @@ public abstract class TransactionAspectSupport implements BeanFactoryAware, Init
 	 * Opaque object used to hold Transaction information. Subclasses
 	 * must pass it back to methods on this class, but not see its internals.
 	 */
-	protected final class TransactionInfo {
+	protected static final class TransactionInfo {
 
 		@Nullable
 		private final PlatformTransactionManager transactionManager;