StringToEnumConverterFactory class from enum value

Update StringToEnumConverterFactory to search superclasses until
Class.isEnum() returns true. This allows conversion when the
enum class is obtained from the enum value:

    public static enum SubFoo {
        BAR { String s() { return "x"; } };
        abstract String s();
    }

    conversionService.convert("BAR", SubFoo.BAR.getClass())

This fix is particularly important when converting collections of
enums.

Issue: SPR-10329

spring-core/src/test/java/org/springframework/core/convert/support/DefaultConversionTests.java

@@ -17,6 +17,7 @@
 package org.springframework.core.convert.support;
 
 import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.*;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -212,6 +213,11 @@ public class DefaultConversionTests {
 		assertEquals(Foo.BAR, conversionService.convert("BAR", Foo.class));
 	}
 
+	@Test
+	public void testStringToEnumWithSubclss() throws Exception {
+		assertEquals(SubFoo.BAZ, conversionService.convert("BAZ", SubFoo.BAR.getClass()));
+	}
+
 	@Test
 	public void testStringToEnumEmptyString() {
 		assertEquals(null, conversionService.convert("", Foo.class));
@@ -226,6 +232,24 @@ public class DefaultConversionTests {
 		BAR, BAZ;
 	}
 
+	public static enum SubFoo {
+
+		BAR {
+			@Override
+			String s() {
+				return "x";
+			}
+		},
+		BAZ {
+			@Override
+			String s() {
+				return "y";
+			}
+		};
+
+		abstract String s();
+	}
+
 	@Test
 	public void testStringToLocale() {
 		assertEquals(Locale.ENGLISH, conversionService.convert("en", Locale.class));