Translate integration test suite to Javacript

[4141done]

Is your feature request related to a problem? Please describe.
Currently the integration test suite has the following issues:

• It is not separate from the image build
• It is tough to understand at first. Especially for new contributors
• New configuration options combined with bash's inflexibility are leading to an increasingly difficult to maintain test suite.

Describe the solution you'd like

1. Decouple image build from integration test run (this will help us clean up the build task and start building multi-arch images)
2. Use a NodeJS-based test runner to perform integration tests

Describe alternatives you've considered
I could be possible to refactor the bash-based runner to handle things better but:

• It seems contributors are more familiar with Javascript than NGINX/Bash. This will lower dependence on the maintainer for tests.
• The new maintainer is more comfortable in JS.