Add plus to test suites

[ciarams87]

Proposed changes

Problem: As a user of NGF that uses an NGINX+ image of NGF
I want the NGINX+ image to be tested with Gateway API's conformance tests and NGINX's non-functional testing
So that I can feel confident that the NGINX+ version of NGF is just as stable as the OSS version.

Solution:

• Update the conformance test suite to support running the tests for plus
• Update the conformance CI pipeline to add plus to the matrix
• Update the NFR test suite to support running the tests for plus

Testing: Ran the conformance tests and the NFR tests using Plus

Please focus on (optional): The AC includes "The release process is updated to include that non-functional tests must be ran against the NGINX+ image in addition to OSS." but we do not have any section in the release process that covers running the NFR tests (as they are currently covered as separate tasks)

Closes #1331

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[kate-osborn]

LGTM

[sjberman]

There appear to be 2 pending checks now, does the new matrix affect the job reporting?

[ciarams87]

There appear to be 2 pending checks now, does the new matrix affect the job reporting?

@sjberman yes, once this is merged I'll update the required checks in the repository settings. Annoyingly, the required checks are defined by job name, and adding a new element to the matrix changes these job names (e.g. Gateway Conformance Tests (latest) -> Gateway Conformance Tests (latest, nginx)). I couldn't add them before the PR was merged because it'll affect the other PRs.

[sjberman]

@ciarams87 I wonder why this is a repo setting and not something that you can set in the pipeline itself...