tests(deck): add deck integration tests

[samugi]

Summary

These tests are meant to catch changes in Kong that result in incompatibilities with decK.

The approach used here is to configure all the bundled plugins in Kong and a few other entities and confirm that deck dump + sync executes without errors.

This new workflow "continues-on-error" instead of producing failures on CI: changes in gateway schemas might have to be merged despite making decK fail, the purpose of this is to notify about such incompatibilities. When those failures are detected, the workflow posts a review in the PR requesting changes, and a link to the failing run.

~The review is then dismissed if new changes are pushed to the PR that make the workflow pass.~ <-- not anymore: branch protection rules prevent this

Checklist

• [x] The Pull Request has tests
• [x] A changelog file has been created under changelog/unreleased/kong or skip-changelog label added on PR if changelog is unnecessary. README.md
• [x] (no) There is a user-facing docs PR against https://github.com/Kong/docs.konghq.com - PUT DOCS PR HERE

Issue reference

KAG-4236

[github-actions[bot]]

decK integration tests

:white_check_mark: passed successfully.

[samugi]

re-drafting to explore the option of using a review (by the bot) instead of a comment, to make the failures more visible when they occur

Edit: done

[team-gateway-bot]

Successfully created cherry-pick PR for master:

• https://github.com/kong/kong-ee/pull/9429