The filter relies on hashing MirbookingOccupant structures in order to
determine if an interaction is to be filtered out by the broker.

Move MirbookingOccupant-related routines into mirbooking-occupant.c and
add corresponding declaration in the header file to reuse them in the
binary.

Add an integration test to make sure that the blacklist filtering is
working.

The new GFile-based output format writer does not support opening
/dev/null in replace mode. Moreover, it's useful to view the output
format when testing to assess if the correct output is produced
(requires meson test -v).

Conflicts:
	tests/meson.build

Make SuperLU optional since we can reasonably rely on having LAPACK
installed.

This in turn fix the cblas package name on Ubuntu.

Add a build-time check since this solver conflicts with the serial
SuperLU implementation.