Add MVP synthetic integration test

[earhart]

Context

We want to have a comprehensive integration test we can run as an action against various deployment environments.

Fixes #1586

What

This change just adds the initial form of the integration test - it's relatively simplistic, but it drives the server through its state changes, it allows the caller to vary the load on the server, and it reports some useful test metrics; it should be sufficient for building the GHA.

Testing

Ran it against a local server, and observed the generated xunit2 report.

Contribution Checklist

• If a Python package was changed, please run make fmt in the package directory.
• If the server was changed, please run make fmt in server/.
• Make sure all PR Checks are passing.

[j3m7]

Not seeing either instructions how to run this during dev or an associated GHA that invokes this. Could you add the GHA's since it's called out on the ticket.

[earhart]

Can I run a GHA against a pending PR? (I was planning to add the GHA once this was in - should be pretty straightforward, except maybe for the xunit2 reporting.)