CI: use docker hub to setup kong in CI

[hbagdi]

Bintray is going away, which means the CI will always be red. The current CI also uses debian packages to set up Kong. The scope here is

• update the CI script to not use Bintray
• use Docker in the CI to run Kong

[mmorel-35]

Maybe would it worth to try to define a github action for this :

• https://docs.github.com/en/actions/creating-actions/creating-a-docker-container-action
• https://docs.github.com/en/actions/creating-actions/creating-a-composite-run-steps-action

This way it could be reused by go-kong and deck, at least.

It would looks like

- name: Set-up Kong
  uses: Kong/setup-kong-action@v1
  env: # the environment variables like KONG_*
  with:
    version: # the version of Kong 

[hbagdi]

@mmorel-35 We could use Github Actions here to solve the problem in the CI but then we will need a separate script to run the tests locally. Instead, if we write a script, we can use that in CI and developer workflow, which helps with keeping different environments consistent.