tests/acceptance: introduce new check-avocado target

tests/acceptance: introduce new check-avocado target

This introduces a new `make` target, `check-avocado`, and adds a
deprecation message about the `check-acceptance` target. This is
a preparation for renaming the `tests/acceptance` folder to
`tests/avocado`.

The plan is to remove the call to the `check-avocado` target one
or two months after the release and leave the warning to force
people to move to the new `check-avocado` target.

Later, the `check-acceptance` target can be removed. The intent
is to avoid a direct impact during the current soft freeze.

Suggested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Willian Rampazzo <willianr@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20211105155354.154864-2-willianr@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>