Inference Extension: Enable conformance tests

[sjberman]

As an NGF developer, I want to run the inference extension conformance tests, to ensure that the feature is working properly.

Acceptance Criteria:

• Gateway API Inference Extension conformance tests are integrated into the pipeline and passing.
• if additional functional tests are necessary due to cases that aren't covered by conformance, create stories for these tests

Design doc: https://github.com/nginx/nginx-gateway-fabric/blob/main/docs/proposals/gateway-inference-extension.md