[FEATURE] Automated testing, build and deployment to PyPi

[jeffreyaven]

Feature Description

Currently CI/CD covers the web site deployment only, need to expand this to cover package updates (any changes to stackql-deploy/**)
. If changes are made to files in this dir tree, then:

1. test that the package version (semver) has been updated (from the previous main version (setup.py and __init__.py)
2. run some basic automated tests (deploying and tearing down basic stacks to AWS, Azure and Google) - provider creds supplied as actions secrets - this can include testing of the marketplace GitHub Action
3. build and publish to PyPi automatically upon merge to main

steps for 3 are:

pip install --upgrade build
pip install twine
python3 -m build
twine upload --config-file .pypirc dist/*

.pypirc contains the access token for PyPi, so this would need to be written in an actions step from an actions secret