Add pairwise testing

Pairwise testing is a test case generation technique based on the observation that most faults are caused by interactions of at most two factors. For BIND such factors are it's configure options and theirs configurations.

These options are processed to a model and this model is processed by the PICT tool, which finds an effective test vector. This test vector configures BIND, build stage follows.

Closes https://gitlab.isc.org/isc-private/bind-qa/-/issues/21.