handle Route conflicts with HTTPRoute.Matches

[lubronzhan]

Fix https://github.com/projectcontour/contour/issues/3608

Now if there is conflicts between HTTPProxy's match, then only the HTTPProxy with

• older creationTimestamp
• alphabetically smaller on namespace/name

, will be chosen as the valid HTTPProxy, other HTTPProxy will be marked as conflict condition

TODO:

• [x] Mark HTTPProxy as conflict condition if needed
• [x] E2E Test

Signed-off-by: lubronzhan [email protected]