Commit window fixes

[kantai]

This PR addresses #2141, by introducing a "burn parent modulus" to allow the stacks-node to detect when a commitment may be missed. This PR also updates the smoothing function to:

min(last_burn, median)

Which is less punitive than mean(min, median)

Type of Change

• Bug fix

Does this introduce a breaking change?

Yes, this changes the wire format for block commits (change is documented in SIP-001), which would lead to a consensus-breaking change.

Documentation updates are probably required -- any mining references we have should be updated to reflect that the smoothing function is changing from

mean(min, median) to min(last_burn, median)

Testing information

There's a few different ways that this is tested:

1. Changes to distribution are unit tested in that module.
2. Changes to the parsing of LeaderBlockCommitOp are tested in that module
3. An integration test for missed block commits is included in the chainstate::coordinator tests. This required adding cfg(test) enabled storage of burn distributions so that the evaluated distribution could be checked after a burn block is processed.

[jcnelson]

This LGTM, but please add the bitmask in the block-commit before merging. Thanks!

[lgalabru]

Looks good to me!

[blockstack-devops]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.