Implement micro performance optimizations

- ClassUtils.isAssignable(): Avoid Map lookup when the type is not a
  primitive.

- AnnotationsScanner: Perform low cost array length check before String
  comparisons.

- BeanFactoryUtils: Use char comparison instead of String comparison.
  The bean factory prefix is '&', so we can use a char comparison
  instead of more heavyweight String.startsWith("&").

- AbstractBeanFactory.getMergedBeanDefinition(): Perform the low cost
  check first. Map lookup, while cheap, is still more expensive than
  instanceof.

Closes gh-34717

Signed-off-by: Olivier Bourgain <olivierbourgain02@gmail.com>

spring-core/src/main/java/org/springframework/core/annotation/AnnotationsScanner.java

@@ -355,6 +355,7 @@ abstract class AnnotationsScanner {
 
 	private static boolean isOverride(Method rootMethod, Method candidateMethod) {
 		return (!Modifier.isPrivate(candidateMethod.getModifiers()) &&
+				candidateMethod.getParameterCount() == rootMethod.getParameterCount() &&
 				candidateMethod.getName().equals(rootMethod.getName()) &&
 				hasSameParameterTypes(rootMethod, candidateMethod));
 	}

spring-core/src/main/java/org/springframework/util/ClassUtils.java

@@ -637,10 +637,11 @@ public abstract class ClassUtils {
 			Class<?> resolvedPrimitive = primitiveWrapperTypeMap.get(rhsType);
 			return (lhsType == resolvedPrimitive);
 		}
-		else {
+		else if (rhsType.isPrimitive()) {
 			Class<?> resolvedWrapper = primitiveTypeToWrapperMap.get(rhsType);
 			return (resolvedWrapper != null && lhsType.isAssignableFrom(resolvedWrapper));
 		}
+		return false;
 	}
 
 	/**