fix all tests in LÖVE v12

fix all tests in LÖVE v12

This is all quite hacky. Many of my tests are unfortunately brittle to
changes in text rendering. Fortunately there's only one test that
currently requires a hacky special case (and a second test I tweaked
slightly to be more robust).

I can't think of a better approach. It doesn't help to standardize the
font, because version changes still come with changes to text-shaping
algorithms even if the font itself is unchanged. I could base all my
assertions on the widths of individual characters, but that would make
the tests much less readable and not express intent as clearly. So here
we are, with hopefully just a few hacky special cases (there might be a
few more as LÖVE v12 advances towards publication, and in further
versions).