Fix Ambient tests and load_config

[bonicim]

Description

Fix test and test infrastructure so that Ambient and Volttron Central properly run and pass. This PR cherry picks the following merge commits from the 'develop' branch:

d322baacf812d8a431125b8ca1eb529d4ba73b5f

bac5447df148a8013950dd6877d77df84b5eba7c

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

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
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules