Inconsistent imports

**Problem:**
I'm having classes generated with imports like:

```
import java.util.Objects;
import org.assertj.core.api.AbstractObjectAssert;
import org.assertj.core.internal.Iterables;
import org.assertj.core.util.Objects;
```

And this results in the compile error:

> 'java.util.Objects' is already defined in a single-type import

**Solution:**

I'd like to just use fully qualified class names instead of import statements.

I see https://github.com/assertj/assertj-assertions-generator/issues/97 requested using imports instead of fully qualified class names. Maybe both should be supported, but it should be configurable which one is being used.

Also it looks like this the use of fully qualified class names was already implemented for 2.2.1 with https://github.com/assertj/assertj-assertions-generator/commit/73d3c5e584e33b1509b058a2707c1ece00ee8bee?

**Versions:**
I'm using assertj-assertions-generator version 2.2.1, assertj-assertions-generator-maven-plugin version 2.2.0, and assertj-core version 3.21.0.

Inizia riproducendo l'errore di compilazione Java generato con le versioni elencate nell'issue, quindi esamina la gestione degli imports e le opzioni di configurazione del generatore. Il lavoro è completato quando le assertions generate non producono più imports in conflitto e la scelta tra imports e nomi di classe completamente qualificati è configurabile.

Scritto dal modello di indicizzazione a partire dal testo della issue.