Reorganization of fv3core analytic test case initialization

[fmalatino]

Purpose

Part of the Pace code vision changes. The initialization of analytic test cases has been altered to generate a modular framework for initializing currently implemented cases and for adding new ones.

Code changes:

• User will now specify in the configuration yaml file that the case is analytic and which specific case is to be initialized.
• A new module which contains all analytic initialization methods which are common to all cases, init_utils.py has been added.
• In initialization.py, the individual classes for analytic test cases have been replaced by a central class, AnalyticInit, which will handle the specification of the case and generation of the driver state
• The files dycore_state.py and geos_wrapper.py have been moved to the locations: fv3core/pace/fv3core/dycore_state.py fv3core/pace/fv3core/wrappers/geos_wrappers.py

Requirements changes:

• User must edit initialization section of yaml file to be read to have the format: initialization: type: analytic config: case: baroclinic

Infrastructure changes:

• N/A

Checklist

Before submitting this PR, please make sure:

• [x] You have followed the coding standards guidelines established at Code Review Checklist.
• [x] Docstrings and type hints are added to new and updated routines, as appropriate
• [x] All relevant documentation has been updated or added (e.g. README, CONTRIBUTING docs)
• [x] For each public change and fix in pace-util, HISTORY has been updated
• [x] Unit tests are added or updated for non-stencil code changes

Additionally, if this PR contains code authored by new contributors:

• [x] The names of all the new contributors have been added to CONTRIBUTORS.md