Move the lcovrc file to the root of the project, so that it’s picked up
by Meson when running `ninja coverage` locally.
See https://github.com/mesonbuild/meson/issues/4628
This won’t affect the code coverage run on the CI, since that explicitly
used the lcovrc file already.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
