tests/py: Add tests involving concatenated ranges

tests/py: Add tests involving concatenated ranges

Very basic testing, just a set definition, a rule which references it
and another one with an anonymous set.

Sadly this is already enough to expose some pending issues:

* Payload dependency killing ignores the concatenated IP header
  expressions on LHS, so rule output is asymmetric.

* Anonymous sets don't accept concatenated ranges yet, so the second
  rule is manually disabled for now.

Signed-off-by: Phil Sutter <phil@nwl.cc>