Guide notebook regression should use a dynamically provisioned github self-hosted runner

[ohinds]

The static self-hosted runner label we use currently is the same for each ec2 instance we spin up, which means there is a race condition where steps in the actions that are running at the same time may be run on an instance created by another action.

We can solve this by dynamically registering the runner, as in
https://github.com/orgs/community/discussions/27204
and
https://www.linkedin.com/pulse/automate-self-hosted-github-runner-creation-using-owain-osborne-walsh/