fix ConfigurationClassParser so that @imported BeanRegistrars use their own class name rather than the class they are imported to

This allows multiple BeanRegistrars to be imported fromm the same Configuration class

fixes #35652

Author: wakingrufus

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

@@ -615,7 +615,7 @@ else if (candidate.isAssignable(BeanRegistrar.class)) {
 						if (registrar instanceof ImportAware importAware) {
 							importAware.setImportMetadata(metadata);
 						}
-						configClass.addBeanRegistrar(metadata.getClassName(), registrar);
+						configClass.addBeanRegistrar(candidateClass.getName(), registrar);
 					}
 					else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
 						// Candidate class is an ImportBeanDefinitionRegistrar ->

spring-context/src/test/kotlin/org/springframework/context/annotation/BeanRegistrarDslConfigurationTests.kt

@@ -24,6 +24,7 @@ import org.springframework.beans.factory.InitializingBean
 import org.springframework.beans.factory.NoSuchBeanDefinitionException
 import org.springframework.beans.factory.config.BeanDefinition
 import org.springframework.beans.factory.getBean
+import org.springframework.beans.factory.getBeanProvider
 import org.springframework.beans.factory.support.RootBeanDefinition
 import org.springframework.mock.env.MockEnvironment
 import java.util.function.Supplier
@@ -77,6 +78,13 @@ class BeanRegistrarDslConfigurationTests {
 		assertThat(context.getBean<Bar>().foo).isEqualTo(context.getBean<Foo>())
 	}
 
+	@Test
+	fun multipleBeanRegistrar() {
+		val context = AnnotationConfigApplicationContext(MultipleBeanRegistrarKotlinConfiguration::class.java)
+		assertThat(context.getBeanProvider<Foo>().singleOrNull()).isNotNull
+		assertThat(context.getBeanProvider<Bar>().singleOrNull()).isNotNull
+	}
+
 	class Foo
 	data class Bar(val foo: Foo)
 	data class Baz(val message: String = "")
@@ -90,6 +98,18 @@ class BeanRegistrarDslConfigurationTests {
 
 	}
 
+	@Configuration
+	@Import(value = [FooRegistrar::class, BarRegistrar::class])
+	internal class MultipleBeanRegistrarKotlinConfiguration
+
+	private class FooRegistrar : BeanRegistrarDsl({
+		registerBean<Foo>()
+	})
+
+	private class BarRegistrar : BeanRegistrarDsl({
+		registerBean<Bar>()
+	})
+
 	@Configuration
 	@Import(SampleBeanRegistrar::class)
 	internal class BeanRegistrarKotlinConfiguration