Add informers and listers for the advanced usages

[zhangtbj]

Changes

In future, the Shipwright Build may be used by other clients, or we will have more advanced usages by leveraging the lister.
Let us add the informers and listers as a complete open-source controller

What I did in the PR:

• Change the generate-codegen.sh to a common name update-codegen.sh
• add informer and lister in the update-codegen.sh
• Reran the update-codegen.sh, the clientset code is updated because the api change (Also compare with how Tekton and Knative do: https://github.com/tektoncd/pipeline/tree/master/hack and https://github.com/knative/serving/tree/master/hack)
• Simplify the generated clientset folder from pkg/client/build to pkg/client directly
• Add the verify-codegen.sh and verify if it is correct now (Of course, this verify-codegen.sh can be executed in each PR verification, but we can do that in future PR):

➜  build git:(add_informer) ✗ ./hack/verify-codegen.sh 

Using code-generator package version, as instructed in the go.mod file
The code-generator package is imported via the pkg/kubecodegen dir
To modify the current version, please modify this in the go.mod

Generating deepcopy funcs
Generating clientset for build:v1alpha1 at github.com/shipwright-io/build/pkg/client/clientset
Generating listers for build:v1alpha1 at github.com/shipwright-io/build/pkg/client/listers
Generating informers for build:v1alpha1 at github.com/shipwright-io/build/pkg/client/informers
Diffing /Users/jordan/gopath/src/github.com/shipwright-io/build against freshly generated codegen
/Users/jordan/gopath/src/github.com/shipwright-io/build up to date.

• Add a README.md in the hack folder to introduce all scripts.
• Refine the test code the use the correct generated clientset package

Submitter Checklist

• [ y ] Includes tests if functionality changed/was added
• [ y ] Includes docs if changes are user-facing
• [ y ] Set a kind label on this PR
• [ y ] Release notes block has been filled in, or marked NONE

/kind enhancement

Release Notes

Add informers and listers for the advanced usages and simplify the generated clientset folder from pkg/client/build to pkg/client directly

[SaschaSchwarze0]

@zhangtbj is not "Simplify the generated clientset folder from pkg/client/build to pkg/client directly" a breaking change that needs special consideration in the release note?

[gabemontero]

/approve

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[zhangtbj]

Thank you @SaschaSchwarze0 , yes, I added the package change in the release note.

[qu1queee]

Reviewing later today, xiexie

[qu1queee]

/lgtm