Draft: POC of KAS tunnel for Workspace Web IDE

Issue: Investigate Alternatives to Kubernetes for Work... (#505764 - closed)

What does this MR do and why?

https://youtu.be/hw5gExP_gvA

How to test

1. Build new KAS
2. gitlab-org/cluster-integration/gitlab-agent!2084 (closed)
3. Build new agent
   1. gitlab-org/cluster-integration/gitlab-agent!2084 (closed)
4. Configure 2 agents
   1. Tunneling agent needs id=1 or you need to change the hardcoded value at gitlab-org/cluster-integration/gitlab-agent!2084 (diffs)
   2. A normal agent for deploying the workspace
5. Build new workspace tools image
   1. gitlab-org/workspaces/gitlab-workspaces-tools!19 (closed)
   2. Copy the agentk built for linux-amd64 into this directory
   3. Copy the .gitlab-agent-token.txt for agent id=1 into this directory
   4. OS=linux PLATFORM=amd64 ENV=local make docker-build-and-publish
6. Run the version of KAS that you built
7. Create a workspace

References

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MR acceptance checklist

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Screenshots or screen recordings

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Related to #505764 (closed)