This (finally) adds backend tests as CPPUNIT tests too. In the
future they'll also be added into LibreOffice directly as a way
to test if the backend is OK, which will be useful especially
for the OpenGL backend, which draw quality depends on the driver.

Currently all the tests are ignored because of the bugs in the
backend, which need to be addressed first and tests then can
be enabled one by one.

The main reason for the test is to identify issues when drawing
is done at a wrong position, which is a very common problem. Also
other types of tests will be added in time, which will have a big
role in the refactoring of VCL that will happen in the future.

Change-Id: I92237d47d49fa0db01b73b8bc39f7a621b65961e
Reviewed-on: https://gerrit.libreoffice.org/70769
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>