Adjust checkForLeaks timeout settings

LeakAwareDataBufferFactory#checkForLeaks automatically waits up to 5
sec for buffers to be released, which could be used as a way of
awaiting on some async logic to complete, and as long as buffers are
released, it shouldn't be long. However, the leak test in
LeakAwareDataBufferFactoryTests actually expects to find a leak, and
always ends up waiting the full 5 seconds.

This change, makes the wait configurable, with the no-arg method
using 0 (no waiting). AbstractLeakCheckingTests uses 1 second by
default since ResourceRegionEncoderTests did fail locally. If more
tests need this, we can adjust the settings.

spring-core/src/test/java/org/springframework/core/codec/ResourceRegionEncoderTests.java

@@ -63,7 +63,7 @@ class ResourceRegionEncoderTests extends AbstractLeakCheckingTests {
 	}
 
 	@Test
-	void shouldEncodeResourceRegionFileResource() throws Exception {
+	void shouldEncodeResourceRegionFileResource() {
 		ResourceRegion region = new ResourceRegion(
 				new ClassPathResource("ResourceRegionEncoderTests.txt", getClass()), 0, 6);
 		Flux<DataBuffer> result = this.encoder.encode(Mono.just(region), this.bufferFactory,

spring-core/src/test/java/org/springframework/core/io/buffer/LeakAwareDataBufferFactoryTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -35,8 +35,7 @@ class LeakAwareDataBufferFactoryTests {
 	void leak() {
 		DataBuffer dataBuffer = this.bufferFactory.allocateBuffer();
 		try {
-			assertThatExceptionOfType(AssertionError.class).isThrownBy(
-					this.bufferFactory::checkForLeaks);
+			assertThatExceptionOfType(AssertionError.class).isThrownBy(this.bufferFactory::checkForLeaks);
 		}
 		finally {
 			release(dataBuffer);