[#1461] Clean compat constants.


Problem description
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This branch is about moving chevah-compat specific constants out of empirical.

This should help with testing and with https://github.com/chevah/compat/pull/12



Why we got into this (5 whys)
=============================

* At the beginning the whole project was a single repo and after a I have split it in independent repos, I did a bad job.


Changes description
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The constants that are used only in elevated tests were moved in chevah.compat.

Update build system to new PQM.

getHostname as staticmethod.


How to try and test the changes
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reviewers @bnickname 

Check that changes make sense.