migrate deprecated/removed Future calls in preparation for vert.x4 migration

In newer RMB release the Vert.x version has been incremented. Since Vert.x update some Future methods became deprecated.
In data-import modules most business-logic is written in composed manner using Future methods. The code is tightly coupled with Future class, that obviously requires a huge rework of existing code base.

These Future methods haven been deprecated and will be removed in Vertx 4.

Quote from https://github.com/vert-x3/wiki/wiki/3.8.0-Deprecations-and-breaking-changes#future-creation-and-completion :

// Deprecated
Future<String> fut = Future.future();
vertx.setTimer(1000, id -> fut.complete("hello");
return fut;

// Now you should do this
Promise<String> promise = Promise.promise();
vertx.setTimer(1000, id -> promise.complete("hello");
return promise.future();

Creating and completing futures is deprecated in Vert.x 3.8 in favor of promises.

Quote from https://github.com/vert-x3/wiki/wiki/4.0.0-Deprecations-and-breaking-changes#%EF%B8%8F-future-sethandler-method-pruning :

☑️ Future setHandler method pruning

https://github.com/eclipse-vertx/vert.x/issues/3329

Vert.x supports multiple handler per future in 4.0. The setHandler method does convey the meaning that a single handler per future can be set and unset and the onComplete, onSuccess, onFailure methods shall be used instead.

The setHandler method usage must be replaced by the onComplete method, e.g

// Before
Future<String> fut = getSomeFuture();
fut.setHandler(ar -> ...);

// After
Future<String> fut = getSomeFuture();
fut.onComplete(ar -> ...);

Vert.x 3.9 deprecates setHandler.

☑️ Future completer method pruning

https://github.com/eclipse-vertx/vert.x/issues/2869

The Future#completer() method is deprecated since Future<T> extends Handler<AsyncResult<T>> for some time now (and the default implementation actually returns this).