add miner diagnostic to block proposal data

[benjamin-stacks]

The exact list of things that should be included in the diagnostics data is up for debate -- please opine on what things might be useful.

https://github.com/stx-labs/core-epics/issues/194

[hstove-stacks]

This plan makes sense to me! My main request is to add unit tests with existing block proposal fixtures (ie hex serialized versions) and do simple round-trip serialization tests. That's helped catch footguns in the past with these kinds of things.

Edit: I'm sure you've seen this, but for one change I just copy/pasted the old implementation into our tests, as a simple way of testing backwards compatibility.

[benjamin-stacks]

My main request is to add unit tests with existing block proposal fixtures (ie hex serialized versions) and do simple round-trip serialization tests.

I already added some such tests for the BlockProposalData specifically. I can also add some more tests to the wrapping type, although I think it wouldn't add any new practical coverage. I may be wrong.

[hstove-stacks]

Ah yes I do now see that we already have that kind of test, so you wouldn't be adding new coverage. Great!