registry.k8s.io: Serve container image layers from AWS by default (make exception when clients are from Google)

Our current logic is to default to Google for traffic not from AWS. We should update the logic to default to AWS if not Google.

This will directly address our top two priorities from our meeting last week.

• -1 : GCP spend HAS to go down (So we stay within budget and make room for other things we need the $$'s for)
• 0 : AWS spend HAS to go up (If we don’t use it, we will end up not getting more)

Our main logic for handling redirects is here: https://github.com/kubernetes/registry.k8s.io/blob/main/cmd/archeio/app/handlers.go#L123-L131

		// check if client is known to be coming from an AWS region
		awsRegion, ipIsKnown := regionMapper.GetIP(clientIP)
		if !ipIsKnown {
			// no region match, redirect to main upstream registry
			redirectURL := upstreamRedirectURL(rc, rPath)
			klog.V(2).InfoS("redirecting blob request to upstream registry", "path", rPath, "redirect", redirectURL)
			http.Redirect(w, r, redirectURL, http.StatusTemporaryRedirect)
			return
		}

I’m suggesting the following or similar:

	// initialize map of clientIP to AWS region
	regionMapper := gcp.NewGCPRegionMapper()
       //... snip ...//
		// check if client is known to be coming from an GCP region
		gcpRegion, ipIsKnown := regionMapper.GetIP(clientIP) // 
		if !ipIsKnown {
			// no region match at GCP, redirect to main upstream registry
			redirectURL := upstreamRedirectURL(rc, rPath)
			klog.V(2).InfoS("redirecting blob request to upstream registry", "path", rPath, "redirect", redirectURL)
			http.Redirect(w, r, redirectURL, http.StatusTemporaryRedirect)
			return
		}

We will need to create a net/cidrs/gcp similar to main/pkg/net/cidrs/aws

It should be nearly the same code, with minor changes to main/pkg/net/cidrs/aws/internal/ranges2go/genrawdata.sh

Swapping out the AWS ranges with GCP ranges:

• https://ip-ranges.amazonaws.com/ip-ranges.json
• https://www.gstatic.com/ipranges/cloud.json (from https://cloud.google.com/compute/docs/faq#find_ip_range)