Refactoring helper funcs out of NetworkState

[akutz]

Proposed Commit Message

Refactoring helper funcs out of network_state

This patch refactors several network, helper functions out of the
network_state.py file and into cloudinit.net. This is in relation
to LP #1855945 and github.com/canonical/cloud-init/pull/1327. The
aforementioned issue requires some refactoring to avoid circular
imports, but it was not proper to do that refactoring in *that*
pull request. Thus this PR is specific to the refactoring and can
be evaluated on its own merits.

LP: #1855945 (partial)

cc @TheRealFalcon

Additional Context

Please see #1327 and #1327 (comment) for more information.

Test Steps

make clean_pyc && PYTHONPATH="$(pwd)" \
  python3 -m pytest -v --log-level=DEBUG \
  tests/unittests/test_net.py \
  tests/unittests/net/test_network_state.py 

I also ran this, and the only failing tests were because I was on a mac:

make clean_pyc && PYTHONPATH="$(pwd)" python3 -m pytest -v tests/unittests

Checklist:

• My code follows the process laid out in the documentation
• I have updated or added any unit tests accordingly
• I have updated or added any documentation accordingly

[akutz]

Oh fun, I suppose I need to actually run all the unit tests locally to find what I broke 😃

[TheRealFalcon]

Thanks for this! To be clear, when I mentioned that ideally we'd move those functions, I wasn't expecting you to do it...but I appreciate it 🙂

[akutz]

Thanks for this! To be clear, when I mentioned that ideally we'd move those functions, I wasn't expecting you to do it...but I appreciate it 🙂

Well, I mean someone was going to end up doing it. Why not me? 😄