Feature: Ability to set desired NetCDF output precision from config

[fmalatino]

Description
This PR introduces methods for setting the desired precision of output when using the netcdf output format. Within a config file, the precision can be specified as follows:

diagnostics_config:
  path: output
  output_format: netcdf
  precision: Float | float32 |float64

The Float option will use whatever is the current value of the PACE_FLOAT_PRECISION environment variable for output precision.
The float32 option will set the output precision to be numpy.float32.
The float64 option will set the output precision to be numpy.float64.
The default option is Float.
The latter two options allow for instances when the desired run precision, as set by PACE_FLOAT_PRECISION, will be different than the required output precision.
If the combination of float64 is used with PACE_FLOAT_PRECISION = 32, a warning will be raised.

How Has This Been Tested?
Tested using the current set of unit tests in the workflow CI

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
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included

[FlorianDeconinck]

LGTM

[oelbert]

👍