INT-3989: WatchServiceDirectoryScanner Improvement

JIRA: https://jira.spring.io/browse/INT-3989,
https://jira.spring.io/browse/INT-3990,
https://jira.spring.io/browse/INT-3988

INT-3989: Add `FileReadingMessageSource.WatchServiceDirectoryScanner`

* Deprecate top-level `WatchServiceDirectoryScanner` because of inconsistency around `Lifecycle` and shared `directory` property
* Copy/paste its logic into the `FileReadingMessageSource.WatchServiceDirectoryScanner` to hide that inconsistency, but still get a gain from the `WatchService` benefits
* Add support for the `StandardWatchEventKinds.ENTRY_MODIFY` and `StandardWatchEventKinds.ENTRY_DELETE` events in the `FileReadingMessageSource.WatchServiceDirectoryScanner`
* Introduce `useWatchService` option to switch to the internal `FileReadingMessageSource.WatchServiceDirectoryScanner`
* Make `CompositeFileListFilter` also as `ResettableFileListFilter`
* Deprecate weird `FileReadingMessageSource.onSend()` method and remove its usage from tests
* Modify `WatchServiceDirectoryScannerTests` for the new logic
* Document changes

Add `MODIFY` and `DELETE` test coverage

Optimize the `filesFromEvents()` logic replacing item with the fresh event sources.
Remove the item from the result set in case of `DELETE` event, because file removal generates both `MODIFY` and `DELETE` events.

* Add `FileReadingMessageSource.setWatchEvents` to allow to listen to the specific events,
not only `CREATE` or all of them.
* Modify tests and docs to reflect the new API

Address PR comments

* Improve `FileReadingMessageSource.setWatchEvents()`
* Add `file.exists()` before adding file from event.

Add more DEBUG logs into the `WatchServiceDirectoryScanner`

With the fact of those logs provide more optimizations:
* Don't register the same directory for watching:
  - use the `ConcurrentMap<Path, WatchKey> pathKeys` to track registrations
  - any modification within the directory causes the `ENTRY_MODIFY` for the directory as well.
    So, skip such an event exactly for the directory during `walkDirectory`
* Add debug logs in case of `ENTRY_DELETE`

spring-integration-amqp/src/test/java/org/springframework/integration/amqp/outbound/AsyncAmqpGatewayTests.java

@@ -203,7 +203,7 @@ public class AsyncAmqpGatewayTests {
 		Message<?> returned = returnChannel.receive(10000);
 		assertNotNull(returned);
 		assertEquals("fiz", returned.getPayload());
-
+		ackChannel.receive(10000);
 		ackChannel.purge(null);
 
 		// Simulate a nack - it's hard to get Rabbit to generate one