Refine null-safety in more modules

This commit refines the null-safety in:
 - spring-jdbc
 - spring-r2dbc
 - spring-orm
 - spring-beans
 - spring-aop

See gh-32475

spring-r2dbc/src/main/java/org/springframework/r2dbc/BadSqlGrammarException.java

@@ -19,6 +19,7 @@ package org.springframework.r2dbc;
 import io.r2dbc.spi.R2dbcException;
 
 import org.springframework.dao.InvalidDataAccessResourceUsageException;
+import org.springframework.lang.Nullable;
 
 /**
  * Exception thrown when SQL specified is invalid. Such exceptions always have a
@@ -52,6 +53,7 @@ public class BadSqlGrammarException extends InvalidDataAccessResourceUsageExcept
 	/**
 	 * Return the wrapped {@link R2dbcException}.
 	 */
+	@Nullable
 	public R2dbcException getR2dbcException() {
 		return (R2dbcException) getCause();
 	}

spring-r2dbc/src/main/java/org/springframework/r2dbc/UncategorizedR2dbcException.java

@@ -51,6 +51,7 @@ public class UncategorizedR2dbcException extends UncategorizedDataAccessExceptio
 	/**
 	 * Return the wrapped {@link R2dbcException}.
 	 */
+	@Nullable
 	public R2dbcException getR2dbcException() {
 		return (R2dbcException) getCause();
 	}

spring-r2dbc/src/main/java/org/springframework/r2dbc/connection/R2dbcTransactionManager.java

@@ -448,6 +448,7 @@ public class R2dbcTransactionManager extends AbstractReactiveTransactionManager
 
 		@SuppressWarnings("unchecked")
 		@Override
+		@Nullable
 		public <T> T getAttribute(Option<T> option) {
 			return (T) doGetValue(option);
 		}

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/binding/BindMarkersFactoryResolver.java

@@ -129,6 +129,7 @@ public final class BindMarkersFactoryResolver {
 
 
 		@Override
+		@Nullable
 		public BindMarkersFactory getBindMarkers(ConnectionFactory connectionFactory) {
 			ConnectionFactoryMetadata metadata = connectionFactory.getMetadata();
 			BindMarkersFactory r2dbcDialect = BUILTIN.get(metadata.getName());