Pull Request Preview Environments for increasing maintainer productivity

I would like to make life easier for Mesh maintainers by implementing [Uffizzi](https://github.com/UffizziCloud/uffizzi) preview environments.
Disclaimer: I work on [Uffizzi](https://github.com/UffizziCloud/uffizzi).

Uffizzi is a Open Source full stack previews engine and our platform is available completely free for Mesh (and all open source projects). This will provide maintainers with preview environments of their PRs in the cloud, allowing them iterate faster and reduce time to merge.

Uffizzi is purpose-built for the task of previewing PRs and it integrates with your workflow to deploy preview environments in the background without any manual steps for maintainers or contributors.

TODO:
- [ ] Intial PoC

The issue names Uffizzi as the proposed service and asks for an initial PoC; start by reviewing Uffizzi's integration documentation and Mesh's pull-request workflow. Clarify the deployment scope and acceptance criteria with maintainers, then verify that a pull request can produce a usable cloud preview without manual maintainer steps.

Written by the indexing model from the issue text.