Nightly backward compatibility testing with e2e tests

[jpraynaud]

Why

We need to run backward compatibility tests to make sure that the current distribution we are working on is compatible (or not) with the previously released distributions. These tests should be run once a day.

What

Create a script that runs the e2e test on all the interesting combinations of signer/aggregator/client/(relay?) versions and records if the e2e test succeeds or fails.

How

• Download the last N (2 or 3) stable distributions binaries
• Create combination of the signer/aggregator/client/(relay?) where all except one are unstable
• Run a e2e test on each combination and record if it succeeds or fails
• Adjust the e2e test parameters for slower execution (slower epochs and slot lengths)
• Create a GitHub Actions workflow with matrix configuration for the combinations
• Schedule the workflow at night
• Manual launch of the workflow with a specific combination and/or different number of previous stable versions?