add diag_manager monitor class and unit tests

[rem1776]

Description

This PR adds a new monitor class that utilizes the diagnostic manager from the FMS fortran library, via the pyFMS python interfaces.

This aims to match up with the existing netcdf monitor object, with the major differences being that fields and axis will need to be explicitly registered. Additionally, the diag monitor can perform a number of reductions on the sent in data such as averaging or taking min/max from what is sent in. These are defined in the diag_table.yaml file, which are created in the test scripts.

One caveat is any written data will be transposed since it is being written from the fortran side.

How has this been tested?

Tested with the added unit tests

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (e.g. add new modules to docs/docstrings/)
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included