Add extension for PropertyResolver#getProperty(String, Class<T>, T)

Allows Kotlin caller to get a non-nullable property,
using a default value when the property is not set.
A method already exists on PropertyResolver which does this,
but takes a Class parameter.
The extension method can eliminate the parameter via reified type,
similar to the other extension methods which exist already.

Closes gh-31523

spring-core/src/main/kotlin/org/springframework/core/env/PropertyResolverExtensions.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -42,6 +42,16 @@ operator fun PropertyResolver.get(key: String) : String? = getProperty(key)
 inline fun <reified T> PropertyResolver.getProperty(key: String) : T? =
 		getProperty(key, T::class.java)
 
+/**
+ * Extension for [PropertyResolver.getProperty] providing a `getProperty<Foo>(...)`
+ * variant returning a non-nullable `Foo` with a default value.
+ *
+ * @author John Burns
+ * @since 6.1
+ */
+inline fun <reified T : Any> PropertyResolver.getProperty(key: String, default: T) : T =
+	getProperty(key, T::class.java, default)
+
 /**
  * Extension for [PropertyResolver.getRequiredProperty] providing a
  * `getRequiredProperty<Foo>(...)` variant.