Move redirect app to the infra/gcp/dns folder

[chizhg]

This is a simple redirection app for redirecting subdomains in knative.dev, which was deployed in the knative-tests project. This PR moves it from our internal codebase to knative/test-infra and configures it to deploy in the knatve-dns project.

I have manually deployed it with make all command and confirmed it's working.

Part of #3134

/cc @kvmware @upodroid

[krsna-m]

Can't we just do the redirect at the DNS layer?

[upodroid]

Can't we just do the redirect at the DNS layer?

No. You want to redirect web requests.

  REDACTED  MCW0CDP3YY  ~  Desktop  Git  $  curl https://testgrid.knative.dev -IL -XGET
HTTP/2 302
content-type: text/html; charset=utf-8
cache-control: no-cache
location: https://testgrid.k8s.io/r/knative-own-testgrid
x-cloud-trace-context: cac0702326b56a9b560066185f209dc9;o=1
date: Mon, 11 Apr 2022 17:24:47 GMT
server: Google Frontend
content-length: 0

HTTP/2 200
x-appengine-log-flush-count: 0
content-type: text/html; charset=utf-8
x-cloud-trace-context: 9589e375c845cbf6c7f1227e5e6d3599
date: Mon, 11 Apr 2022 17:24:47 GMT
server: Google Frontend
content-length: 9711

[upodroid]

LGTM

[knative-prow]

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