Move update servers to SRE

[jemrobinson]

✅ Checklist

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⤴️ Summary

• Add Dockerised apt proxy server to the SRE
• Remove update server VM from SHM
• Remove unused networking and components from SHM

Note that the workspaces must be deployed after the apt-proxy is fully configured. To achieve this we make the workspace dependent on the apt-proxy private DNS hostname, which itself is dependent on the apt-proxy private IP address which is not available until the container reaches "Running" status.

🌂 Related issues

Closes #1837. Closes #1832.

🔬 Tests

Tested on fresh SHM and SRE deployment

[JimMadge]

Would it be sensible to merge #1820 into this?

[jemrobinson]

I think they're independent. Is #1820 ready to merge?

[JimMadge]

I think there will be some conflicts (hopefully easy to fix 🤞). config.tags and config.context don't exist any more, for example.

[JimMadge]

Is #1820 ready to merge?

It definitely breaks the code. So we could either finish the fixes in #1839 first, or merge it and continue #1839. What do you think?

[jemrobinson]

• This PR (Move update servers to SRE #1847) is ready to merge as-is
• Move pulumi context settings and persistent data #1820 would break develop if merged as-is
• Pulumi storage fixes, including adding encryption key #1839 fixes some of those problems but hasn't been tested

I suggest we do the following:

• Merge Move update servers to SRE #1847 once it's been reviewed
• Merge Pulumi storage fixes, including adding encryption key #1839 into Move pulumi context settings and persistent data #1820 whenever you feel like it's ready (before or after testing)
• We co-work on testing Move pulumi context settings and persistent data #1820 once you think it's in a working state
• I'm happy to fix merge issues on Move pulumi context settings and persistent data #1820 that are caused by merging Move update servers to SRE #1847.

[craddm]

LGTM