Add verify script to detect dead code

[adrianmoisey]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

Dead code causes the outputted Go binary to be larger. Upstream kubernetes recently put effort into ensuring that Kubernetes doesn't include dead code.
We should copy this, if reasonable to do so, to save storage and bandwidth costs.

Which issue(s) this PR fixes:

Fixes #8270

Special notes for your reviewer:

I've modified the verify script to run all verify-.shscripts for the VPA. It seems that the codegen hasn't been run in a while, which I'll fix in another PR

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[k8s-ci-robot]

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• hack/OWNERS [adrianmoisey]
• vertical-pod-autoscaler/OWNERS [adrianmoisey]

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[jackfrancis]

I know this is going to be annoying, but is there any way we could put this in the root hack/ directory and re-use between CA and VPA? CA has stuff, too

$ GOLDFLAGS=-dumpdep go build -C cluster-autoscaler -ldflags=-dumpdep -o cluster-autoscaler 2>&1 | grep "\->" | /Users/jackfrancis/go/bin/whydeadcode
text/template.(*state).evalField reachable from:
	 text/template.(*state).evalFieldChain
	 text/template.(*state).evalCommand
	 text/template.(*state).evalPipeline
	 text/template.(*state).walk
	 text/template.(*Template).execute
	 html/template.(*Template).Execute
	 golang.org/x/net/trace.RenderEvents
	 golang.org/x/net/trace.Events
	 golang.org/x/net/trace.Events·f
	 golang.org/x/net/trace.init.0
	 golang.org/x/net/trace..inittask
	 go:main.inittasks
	 _

k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.(*addressableValue).Method reachable from:
	 type:k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.addressableValue
	 type:func(k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.MarshalOptions, *k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.Encoder, k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.addressableValue) error
	 type:k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.typedArshaler[k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.MarshalOptions,k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.Encoder]
	 type:[]k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.typedArshaler[k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.MarshalOptions,k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.Encoder]
	 type:k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.typedArshalers[k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.MarshalOptions,k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.Encoder]
	 type:*k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.typedArshalers[k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.MarshalOptions,k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.Encoder]
	 type:k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.MarshalOptions
	 type:func(k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.MarshalOptions, *k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.Encoder) error
	 type:k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.MarshalerV2
	 type:*k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.MarshalerV2
	 k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json.init
	 k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json..inittask
	 go:main.inittasks
	 _

github.com/GoogleCloudPlatform/k8s-cloud-provider/pkg/cloud/meta.(*ServiceInfo).Methods reachable from:
	 type:*github.com/GoogleCloudPlatform/k8s-cloud-provider/pkg/cloud/meta.ServiceInfo
	 github.com/GoogleCloudPlatform/k8s-cloud-provider/pkg/cloud/meta.init.0
	 github.com/GoogleCloudPlatform/k8s-cloud-provider/pkg/cloud/meta..inittask
	 go:main.inittasks
	 _

github.com/google/go-cmp/cmp/internal/value.appendTypeName reachable from:
	 github.com/google/go-cmp/cmp.formatOptions.FormatType
	 github.com/google/go-cmp/cmp.formatOptions.FormatDiff
	 github.com/google/go-cmp/cmp.(*defaultReporter).String
	 github.com/google/go-cmp/cmp.Diff
	 k8s.io/cloud-provider-gcp/providers/gce.(*Cloud).ensureInternalLoadBalancer
	 k8s.io/cloud-provider-gcp/providers/gce.(*Cloud).EnsureLoadBalancer
	 type:*k8s.io/cloud-provider-gcp/providers/gce.Cloud
	 type:k8s.io/cloud-provider-gcp/providers/gce.Cloud
	 k8s.io/cloud-provider-gcp/providers/gce.CreateGCECloud
	 k8s.io/cloud-provider-gcp/providers/gce.newGCECloud
	 k8s.io/cloud-provider-gcp/providers/gce.init.0.func1
	 k8s.io/cloud-provider-gcp/providers/gce.init.0.func1·f
	 k8s.io/cloud-provider-gcp/providers/gce.init.0
	 k8s.io/cloud-provider-gcp/providers/gce..inittask
	 go:main.inittasks
	 _

[adrianmoisey]

I know this is going to be annoying, but is there any way we could put this in the root hack/ directory and re-use between CA and VPA?

My preference is to not do that, since the VPA and CA operate quite differently (ie: VPA has 3 binaries).
Given the simplicity of this script, I think duplicating it is fine