Add util methods to manipulate configuration files in the test

Description

Currently, it's possible to edit configuration files in the @Config.
It's also possible to modify configuration files using ${karaf.etc} and getting the stream but it's not convenient.
We should provide convenient methods to manipulate configuration/configuration files directly in the tests.

Environment

None

Assignee

Jean-Baptiste Onofre

Reporter

Jean-Baptiste Onofre

Labels

None

Components

Priority

Major
Configure