Legacy chain check and tests

[oxarbitrage]

Motivation

We need to have a check after Nu5 activation when zebra starts to make sure we are not following a legacy chain. Close #2308

Solution

Implement what is detailed in the ticket: #2308

Review

I know a lot here can be improved so i will like @jvff to make an initial review before passing it into @teor2345 later on.

Reviewer Checklist

• Code implements Specs and Designs
• Tests for Expected Behaviour
• Tests for Errors

[jvff]

Looks good! I added a few suggestions to the code, and an example of a different way to organize the tests, but they're all optional 👍

[teor2345]

This looks like a good start - the overall check and structure is pretty good.

Before the next review, let's try to:

• fix bugs in the legacy chain check
• simplify the code and module structure
• change the legacy chain check and proptest strategies so they are easier to test

I also made some suggestions to improve the panic message. We could make them into another ticket. Or if you have time, you could do them after the other changes are done.

[oxarbitrage]

I think is ready for a second round of review. The panic changes were not done, i think we should do them in a new ticket with lower priority. I didn't updated #1841 yet, i think the rest is more or less covered even if sometimes not exactly as suggested.

[teor2345]

I think we're pretty good here, just a few things we could tweak, and a small bug fix.

You might want to check with @conradoplg about the chain proptest strategies, he's also fixing some issues.

[teor2345]

This looks good now, but it changes the cached state tests, so it is blocked by #2402.

[teor2345]

The blockers have all merged.

There's no easy way to test this branch merged with the latest main, so I'm just going to go ahead and merge, and then check that it works.

If it fails someone should revert and re-open the PR.

[teor2345]

This appears to work locally on mainnet and testnet, with and without cached state, and before and after the mandatory checkpoint.