Remove topics and associated ACLs on deployment if topic removed.

[big-andy-coates]

When deploying later versions of a spec, it may be the case that a topic has been removed. Leaving this lying around would result in some of the issues SpecMesh is trying to avoid, e.g. topics that no one knows if they're still important. Hence we should remove them, and their associated ACLs.

The tricky bit here is that applications may create their own internal topics not in the spec: e.g. a streams app might create repartition and changelog topics. I'm not sure we want to have to define all of these in the spec. However, I think it's ok to limit such creations to _private topics.

Our clean up rules are then simple:

1. remove any _public and _protected topics, and their ACLs, that aren't in the spec.
2. leave any _private topics that are not in the spec.

This works well as its the public and protected topics that are hand to know if its OK to remove down the line. By forcing their removal we ensure dev/qa/staging environments have been updated and hence users should have confidence no one needs the removed topic. (Plus removing it from the spec should cause builds of downstream domains to fail .... though need to work out how this would work).

Leaving old private topics around isn't so much of an issue, as:

1. no one else but the domain can access them,
2. so engineers can easily determine which the app is still using and delete the old.