Add Istio k8s client

[stefanprodan]

This PR replaces the knative pkg with an Istio client generated based on the v1.1.0 protos. Only the Virtual Service CRD is implemented from the networking/v1alpha3 group.

Fix: #79

[codecov-io]

Codecov Report

Merging #80 into master will increase coverage by 0.03%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master      #80      +/-   ##
==========================================
+ Coverage   54.53%   54.56%   +0.03%     
==========================================
  Files          13       13              
  Lines        1533     1532       -1     
==========================================
  Hits          836      836              
+ Misses        557      556       -1     
  Partials      140      140

Impacted Files	Coverage Δ
pkg/controller/deployer.go	58.7% <ø> (ø)	⬆️
pkg/router/istio.go	80% <ø> (ø)	⬆️
pkg/controller/controller.go	7% <ø> (+0.04%)	⬆️
pkg/router/factory.go	0% <0%> (ø)	⬆️

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[huydinhle]

Did this get generated or you did this by hand? this is for my learning 😅

[stefanprodan]

All was done by hand :(

[huydinhle]

👍 This is nice. I assume this will solve our problem with CORS policy(#58) that is unsupported currently in the CanaryService object as well ?

[stefanprodan]

Yes this will allow us to ship CORS support. What's more important is that we can now control the upgrade path to Istio 1.1 without depending on some other project that could chose to delay the upgrade for months.