Add supports for categorize test cases with TestNG Groups

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#### I'm submitting a ...
- feature request

#### What is the current behavior?

Recently, I came across the problem that I wasn't able to check the results of test case group wise when I executed the same test case in different groups in different Jenkins jobs.

Below is the scenario:
1. Test case **A** is a part of group UK and US.
2. Trigger Jenkins job **J** to execute test case **A** in Jenkins job **J1** as a part of UK and in Jenkins job **J2** as a part of US.
4. Copy allure artifacts of **J1** and **J2** in **J** and merge the report using allure Jenkins plugin.

**Results**: Jenkins job **J** merged test case **A** results as a history.

#### What is the expected behavior?

I want to see the execution results group-wise for clear understanding.

#### Please tell us about your environment:

No need to specify as its feature request.

Comienza revisando la integración de TestNG y el escenario de merge de Jenkins descrito en el issue. Determina cómo se representan actualmente la pertenencia a grupos y los resultados fusionados, y luego define pruebas que distingan el mismo caso ejecutado en los grupos UK y US; se considerará completado cuando el informe fusionado exponga esas ejecuciones por grupo.

Escrito por el modelo de indexación a partir del texto del issue.