Ability to rename classes with TestNG

#### I'm submitting a ...
- [ ] bug report
- [*] feature request
- [ ] support request => Please do not submit support request here, see note at the top of this template.

#### What is the current behavior?

Allure groups suites into sub-suites, which, in case of TestNG, are full class names (with their packages).

#### What is the expected behavior?

As far as I understand, Allure has an ability to use custom class names with JUnit. In JUnit, classes can be renamed with `@DisplayName` annotation. In TestNG, there's no such annotation, thus, I'd like to have something like Allure's `@Description` annotation be applicable to class names. For example,
```
@Description("Class Name Without Package")
public class TestClass
```

#### What is the motivation / use case for changing the behavior?

Some projects have very long package names, which are redundant for reports.

#### Please tell us about your environment:
| Allure version | 2.8.1 |
| --- | --- |
| Test framework | testng@6.8 |
| Allure integration | allure-testng@2.13.2 |
| Generate report using | allure-maven@2.10.0 |

#### Other information

まず TestNG 統合の場所を特定し、Allure が JUnit のカスタムクラス名をどのように処理しているかを比較します。クラスレベルの説明または同等のものが、既存の TestNG のグループ化を維持しながらスイート名にどのような影響を与えるべきかを定義し、その後、生成されたレポートでパッケージなしのカスタム名が使用されることを確認します。

索引モデルが issue の本文から書いたものです。