VirtualService simple merging of http routes at Gateway

[rshriram]

Replica of PR from #8113

Signed-off-by: Shriram Rajagopalan shriramr@vmware.com

[istio-testing]

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[codecov]

Codecov Report

Merging #8114 into master will increase coverage by 1%.
The diff coverage is 62%.

@@           Coverage Diff           @@
##           master   #8114    +/-   ##
=======================================
+ Coverage      71%     71%    +1%     
=======================================
  Files         374     374            
  Lines       32994   33015    +21     
=======================================
+ Hits        23212   23323   +111     
+ Misses       8763    8677    -86     
+ Partials     1019    1015     -4

Impacted Files	Coverage Δ
pilot/pkg/networking/util/util.go	26% <ø> (ø)	⬆️
pilot/pkg/networking/core/v1alpha3/httproute.go	25% <0%> (+1%)	⬆️
pilot/pkg/networking/core/v1alpha3/gateway.go	0% <0%> (ø)	⬆️
pilot/pkg/networking/core/v1alpha3/route/route.go	35% <86%> (+6%)	⬆️
mixer/adapter/rbac/util.go	56% <0%> (-13%)	⬇️
mixer/pkg/protobuf/yaml/resolver.go	59% <0%> (-1%)	⬇️
pilot/pkg/serviceregistry/kube/controller.go	66% <0%> (ø)	⬇️
mixer/pkg/protobuf/yaml/pool.go	100% <0%> (ø)	⬆️
pilot/pkg/serviceregistry/consul/monitor.go	81% <0%> (ø)	⬆️
mixer/adapter/prometheus/prometheus.go	100% <0%> (ø)	⬆️
... and 15 more

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[rshriram]

/test e2e-mixer-no_auth