ProvisionController support for SharedInformers

[zcahana]

This PR adds support for running the ProvisionController with SharedInformers.

This is achieved by introducing a new constructor, NewProvisionControllerWithConfig() that enables to optionally pass in shared informers; The existing constructor, NewProvisionController(), as well as its behavior, are left as they were.

Resolves #546.

[k8s-ci-robot]

Thanks for your pull request. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please follow instructions at https://git.k8s.io/community/CLA.md#the-contributor-license-agreement to sign the CLA.

It may take a couple minutes for the CLA signature to be fully registered; after that, please reply here with a new comment and we'll verify. Thanks.

---

• If you've already signed a CLA, it's possible we don't have your GitHub username or you're using a different email address. Check your existing CLA data and verify that your email is set on your git commits.
• If you signed the CLA as a corporation, please sign in with your organization's credentials at https://identity.linuxfoundation.org/projects/cncf to be authorized.
• If you have done the above and are still having issues with the CLA being reported as unsigned, please email the CNCF helpdesk: [email protected]

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository. I understand the commands that are listed here.

[zcahana]

@k8s-ci-robot I've signed the CLA.

[zcahana]

/cc @wongma7

[zcahana]

I've refactored the code to be consistent with the functional options pattern:

• Introduced 3 new option functions: ClaimsInformer(), VolumesInformer(), and ClassesInformer(),
  to be used with NewProvisionController().
• Removed the NewProvisionControllerWithConfig() constructor mentioned in the beginning of this PR.

[zcahana]

@wongma7 did you get a chance to look at this?

[rootfs]

/assign @jsafrane
wait till #578 is resolved

[zcahana]

I've removed the commit which vendored the additional client-go/informers/* packages (as these were added as part of #578), and rebased.

[jsafrane]

/lgtm

[jsafrane]

/approve no-issue
Checking if there is merge bot...