INT-3749: Get rid of IECA logic

JIRA: https://jira.spring.io/browse/INT-3749

Since `IntegrationEvaluationContextAware` isn't so "context-free" resource like `BeanFactory`
 and `ApplicationContext`, but just a specific bean in the context, we can't follow with `BeanPostProcessor` logic - bad architecture by level of responsibility.
 Therefore we should follow with standard Dependency Injection mechanism to retrieve `evaluationContext` for the particular component.

 Since we can't rely on the `@Autowired` because SI can be used from the raw XML configuration,
 we use utility method instead. The pattern to get the proper `integrationEvaluationContext` is:
 ```
 @Override
 protected void onInit() throws Exception {
 		super.onInit();
 		this.evaluationContext = ExpressionUtils.createStandardEvaluationContext(getBeanFactory());
 }
 ```

spring-integration-sftp/src/test/java/org/springframework/integration/sftp/inbound/SftpInboundRemoteFileSystemSynchronizerTests.java

@@ -109,7 +109,9 @@ public class SftpInboundRemoteFileSystemSynchronizerTests {
 		filters.add(patternFilter);
 		CompositeFileListFilter<LsEntry> filter = new CompositeFileListFilter<LsEntry>(filters);
 		synchronizer.setFilter(filter);
-		synchronizer.setIntegrationEvaluationContext(ExpressionUtils.createStandardEvaluationContext());
+		synchronizer.setBeanFactory(mock(BeanFactory.class));
+		synchronizer.afterPropertiesSet();
+
 		SftpInboundFileSynchronizingMessageSource ms = new SftpInboundFileSynchronizingMessageSource(synchronizer);
 		ms.setAutoCreateLocalDirectory(true);
 		ms.setLocalDirectory(localDirectoy);