Fix Helm chart namespace and handle webhooks certificates creation

[kvaps]

• Remove namespace options, use {{ .Release.Namespace }} instead
• Use kube-webhook-certgen for generating certificates and inject them into webhook configuration

[chrislusf]

Thanks for the fix! Please split similar PRs later if there are more than one changes.

[okgolove]

Hello @kvaps. I've noticed at the very first install with enabled webhook deployment fails to start. The workaround is to disable, install, then enable again.