🐛 use self-signed certificate for the virtualcluster webhook server

[charleszheng44]

What this PR does / why we need it:

Use a self-signed certificate for the virtual cluster webhook. See issue #125 for more details.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
fixes #125

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This pull-request has been approved by: charleszheng44

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[charleszheng44]

@vincent-pli The VC should be able to run on Kind after this PR is merged.

@christopherhein
@Fei-Guo

[christopherhein]

@charleszheng44 do you think VC should be managing these resources for the user? or should we be prescribing that the operator use cert-manager or manage their cluster certificates themselves?

I know cert-manager itself did a lot of cludgy work just to enable this type of seamless setup process for auto-deploying their own certs and it was fairly painful to write and maintain. It feels like we could make this easier with just supplying configs to use cert manager auto-injection and then we could rip out all this setup code and expect that if they aren't using cert-manager that they have an existing flow for certs and thus can just use that path.

[christopherhein]

Code looks fine otherwise more just commenting on the overall approach.

[charleszheng44]

@christopherhein I prefer using cert-manager to manage all certifications. But do you think it would be an overkill to deploy cert-manager to just manage the certification for the webhook server. Or we can use the cert-manager to manage all certifications for VC control plane components. However, I think we will use the CAPN to replace the VC native mode, and maybe we should import the cert-manager by then? We can use the cert-manager to manage certifications for all components (i.e., CAPN control plane components and VC webhook servers).

[christopherhein]

@charleszheng44 mmk, that seems like a reasonable approach instead.

/lgtm