add istio patch to fix xds push

[johnlanni]

Ⅰ. Describe what this PR did

The previous hack implementation caused LDS to be pushed empty

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov-commenter]

Codecov Report

Merging #52 (e217cd8) into main (268c733) will decrease coverage by 4.82%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #52      +/-   ##
==========================================
- Coverage   29.63%   24.80%   -4.83%     
==========================================
  Files          27       24       -3     
  Lines        4330     4076     -254     
==========================================
- Hits         1283     1011     -272     
- Misses       2986     3008      +22     
+ Partials       61       57       -4     

Impacted Files	Coverage Δ
pkg/ingress/kube/annotations/canary.go	18.42% <0.00%> (-20.43%)	⬇️
pkg/ingress/kube/annotations/ip_access_control.go	87.50% <0.00%> (-12.50%)	⬇️
pkg/ingress/kube/annotations/loadbalance.go	89.18% <0.00%> (-10.82%)	⬇️
pkg/ingress/kube/annotations/parser.go	58.59% <0.00%> (-7.65%)	⬇️
pkg/ingress/kube/annotations/timeout.go
pkg/ingress/kube/annotations/local_rate_limit.go
pkg/ingress/kube/annotations/header_control.go
pkg/ingress/kube/ingressv1/controller.go	3.71% <0.00%> (+<0.01%)	⬆️
pkg/ingress/kube/ingress/controller.go	3.72% <0.00%> (+<0.01%)	⬆️
pkg/ingress/kube/annotations/downstreamtls.go	88.23% <0.00%> (+3.30%)	⬆️
... and 1 more

[SpecialYang]

Don't understand why use the mcp generator directly. Since the resources were sent to mcp store, why not use the xds generator?

[johnlanni]

Don't understand why use the mcp generator directly. Since the resources were sent to mcp store, why not use the xds generator?

Although these two Resource types are all convert to []Any in the DiscoveryResponse, xds generator generates the Resource which is defined by envoy's api in discovery/v3, and mcp generator generates the Resource which is defined by istio's api in mcp/v1alpha1.

[SpecialYang]

What's protocol between envoy and istio? xds or mcp-over-xds?

[johnlanni]

What's protocol between envoy and istio? xds or mcp-over-xds?

I understand your doubts, in fact, istio will not call pushMcpXds here, only higress will, here is higress reuse the logic related to xds

[SpecialYang]

We should reconsider this way in the future. It's better to build our xds server.