conformance: test gateway referencing an unexisting tls secret #1318
Description
What would you like to be added:
A new conformance test case testing the presence of the status ResolvedRefs condition failed with the reason InvalidCertificateRef should be added to the conformance test suite.
To do so, the test case should create a gateway that references a non-existing TLS secret and check the failed ResolvedRefs condition is added to the corresponding listener status with the reason InvalidCertificateRef.
Why this is needed:
This is needed to ensure that when the referenced secret does not exist, the listener status is set accordingly.