DOC-149 multi namespace docs update

[janekbaraniewski]

Fixes DOC-149

Currently if user tries to just install using example vcluster.yaml provided in multi namespace docs, it will cause crashloop of vCluster pod on k8s clusters that don't have cert-manager installed.

This PR:

• deduplicates example vcluster.yaml used in this doc
• updates multi namespace example using cert-manager to be a more comprehensive, step by step guide

Preview: here

[netlify[bot]]

✅ Deploy Preview for vcluster-docs-site ready!

Built without sensitive environment variables

Name	Link
🔨 Latest commit	f208708d37888ec61e563003cdd17d56746d981c
🔍 Latest deploy log	https://app.netlify.com/sites/vcluster-docs-site/deploys/666820c7e59ac80008bba054
😎 Deploy Preview	https://deploy-preview-143--vcluster-docs-site.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[deniseschannon]

Tip: Instead of putting in screenshots, you can take the netlify URL, append /docs and navigate to the page and put that link into the comments.

[janekbaraniewski]

@deniseschannon cool, thx, will remember about that! here is the link: https://deploy-preview-143--vcluster-docs-site.netlify.app/docs/vcluster/deploy/topologies/multi-namespace-mode