feat: proposal pre/post test steps

[usmanmani1122]

closes: #xxxx

@agoric/synthetic-chain library

• Added pre/post test steps support. This is needed to be able to run a follower in a separate container to monitor the chain under load
• Enabled host network for the test container to allow communication between containers. We can also make a separate network bridge but the host network seems sufficient as we can assign different ports (than the default ones) to the follower
• Added a file as volume mount from host to allow communication between containers without needing custom web servers in containers

A successful github action run using these changes:
https://github.com/Agoric/agoric-sdk/actions/runs/12596102473
agoric-sdk change can be seen here