INT-4154: Merge Files Java DSL

JIRA: https://jira.spring.io/browse/INT-4154

* Move `Transformers` for files to the `Files` factory
* Remove `@Deprecated` methods
* Fix `FilesTests` for new packages and removed methods like `.handleWithAdapter()`

Provide JavaDocs for File DSL and implement some new methods like `chmod()` and `renameFunction()`

Fix race condition in the `ScriptsTests` when even small time window delay may lead us to one more message in the queue

spring-integration-scripting/src/test/java/org/springframework/integration/scripting/dsl/ScriptsTests.java

@@ -178,13 +178,11 @@ public class ScriptsTests {
 		assertThat(payload, Matchers.instanceOf(Date.class));
 
 		// Some time window to avoid dates collision
-		Thread.sleep(500);
+		Thread.sleep(2);
 
 		assertTrue(((Date) payload).before(new Date()));
 
 		assertNotNull(this.messageSourceChannel.receive(20000));
-
-		assertNull(this.messageSourceChannel.receive(10));
 	}
 
 	@Configuration