Run stmgr hostconfig-check tests

Basically moves draft MR stboot!174 (closed) from stboot repo to here. If we want to detect incompatibilities early from the checked-in files, we could consider running stmgr tests with stboot HEAD at some point.

Note that we should already have unit tests that covers the corner cases in the checked in files here, which is why I'm not so fond of adding more unit tests in stboot based on these files. For me, the point of this MR is to get usage of stmgr running in our CI, and for there to be a place where users can contribute selected host configuration publicly if it makes sense.

Closes stboot#162 (closed).