Ensure classes are defined in their own files

Ensure that all classes are defined in their own files. Mostly classes
have been changed to inner-types.

Issue gh-8945

core/src/test/java/org/springframework/security/access/expression/AbstractSecurityExpressionHandlerTests.java

@@ -69,19 +69,19 @@ public class AbstractSecurityExpressionHandlerTests {
 		assertThat(parser == this.handler.getExpressionParser()).isTrue();
 	}
 
-}
+	@Configuration
+	static class TestConfiguration {
 
-@Configuration
-class TestConfiguration {
+		@Bean
+		Integer number10() {
+			return 10;
+		}
 
-	@Bean
-	Integer number10() {
-		return 10;
-	}
+		@Bean
+		Integer number20() {
+			return 20;
+		}
 
-	@Bean
-	Integer number20() {
-		return 20;
 	}
 
 }

core/src/test/java/org/springframework/security/util/FieldUtilsTests.java

@@ -42,20 +42,20 @@ public class FieldUtilsTests {
 		}
 	}
 
-}
+	@SuppressWarnings("unused")
+	static class TestClass {
 
-@SuppressWarnings("unused")
-class TestClass {
+		private String protectedField = "x";
 
-	private String protectedField = "x";
+		private Nested nested = new Nested();
 
-	private Nested nested = new Nested();
-
-}
-
-@SuppressWarnings("unused")
-class Nested {
-
-	private String protectedField = "z";
+	}
+
+	@SuppressWarnings("unused")
+	static class Nested {
+
+		private String protectedField = "z";
+
+	}
 
 }