tests/functional: Convert the m68k nextcube test with tesseract

tests/functional: Convert the m68k nextcube test with tesseract

The code that handles running of tesseract needs to be tweaked a little
bit to be able to run without the functions from avocado.utils, and
while we're at it, drop some legacy stuff that was still there due to
Tesseract 3 support that we already dropped a while ago.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240830133841.142644-29-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>