Gateway API: conformance test for behavior of Contour on multiple Route with conflicts in Match

[lubronzhan]

Please describe the problem you have [A clear, concise, description of the problem you are facing. What is the problem that feature X would solve for you?] Originate from discussion here

When multiple Route objects that have conflict on Match, instead of dropping the whole Route object, Contour should still consider the Route PartiallyInvalid: true, and still add remaining not conflicted sub route to the DAG. This is what upstream expects