Transition pynio to cfgrib for wgrib2 engine.

[christinaholtNOAA]

Transition from the deprecated pynio to cfgrib for wgrib2 loading into an xarray object.

The need for this change is driven by a couple of immediate requirements:

• The version of python needs to be updated as 3.7 is no longer supported, posing a security risk. That cannot be done with this version of pynio.
• The environment containing pynio cannot be installed from open-use conda-forge channels.

As part of this extensive upgrade, I've also included additional tooling and unittests to help ensure quality. The current coverage is set to 75%. The intent is to follow up this PR with additional tests for 100% coverage.

New tools include:

• mypy for typechecking
• ruff for linting (replacing pylint), formatting (new), and list sorting (new)
• pytest-cov for a coverage report

All of these tools can be run with a new Makefile that includes helpful targets for a more automated experience with the test framework.

[maddenp-cu]

Just a few more ideas, to take or leave.

I'll circle back tomorrow to your outstanding responses to my previous review.

[maddenp-cu]

Almost exclusively copy-editing suggestions, and only for text in diff regions or nearby -- I didn't go hunting in unchanged parts of files.

In addition to these, I'll note that there's a variety of keyword vs key word, and "Skew-T" is all over the place: "skewt", "SkewT", "Skew-T", "Skew T", etc. It could be worth (maybe someday?) normalizing these to make finding related code and comments easier. Many developers will think to do case-insensitive searching, but fewer will use regexes to make whitespace (much less hyphenation) optional. Just doing due diligence by pointing this out.

[maddenp-cu]

I think that's all I've got. I'm happy to respond to any @mentions and help with anything, and none of my comments should be considered blockers, just ideas/suggestions. Heroic effort here bringing this codebase up-to-date!