Merge pull request #414 from lsst/tickets/DM-34105

DM-34105: Move some code to pipe_base to reduce afw dependency on core middleware

Author: timj

doc/changes/DM-34105.feature.rst

@@ -0,0 +1,4 @@
+* `lsst.obs.base.Instrument` is now a subclass of `lsst.pipe.base.Instrument`. This simplifies the dependencies of ``ctrl_mpexec`` by removing any need to understand camera geometry or curated calibrations.
+* As part of this move the ``butler register-instrument`` command has been moved to ``pipe_base``.
+* The ``PackagesFormatter`` has been moved to ``daf_butler`` and the ``PexConfigFormatter`` has been moved to ``pipe_base`` since both of these are required by ``ctrl_mpexec``.
+* ``lsst.obs.base.utils.getInstrument`` has been replaced with ``Instrument.from_string``.