MAINTAINERS: Add an entry to review Avocado based acceptance tests

MAINTAINERS: Add an entry to review Avocado based acceptance tests

    Acceptance tests can test any piece of the QEMU codebase.
    As such, the directory holding them does not belong to a specific
    subsystem with designated maintainers.

    Each subsystem covered by a test is welcomed to add the test path
    to its section.
    See for example commits 71b290e70, b11785ca2 or 5d480ddde.

Add an entry for to allow reviewers to be notified when acceptance /
integration tests are added or modified.
The designated reviewers are not maintainers, subsystem maintainers
are expected to merge their tests.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Eduardo Habkost <ehabkost@redhat.com>
Acked-by: Cleber Rosa <crosa@redhat.com>
Message-Id: <20200129212345.20547-30-philmd@redhat.com>
Message-Id: <20200605165656.17578-1-philmd@redhat.com>