change(rpc): Refactor get block template RPC into stages

[teor2345]

Motivation

To implement long polling, we need to repeat some parts of the get block template RPC.

But currently the RPC function is very large, and in no specific order.

This refactor does not change any Zebra functionality, except that the long poll ID now tracks all mempool transactions.

Solution

Functional Changes:

• Split fetching mempool transactions out, include them in long poll id

Refactors:

• Move and rename height_from_signed_int()
• Move get_block_template() support functions to a submodule
• Split initial checks into their own functions
• Split state fetch into its own function
• Refactor coinbase generation
• Split default root calculation into a separate function
• Split out a generate coinbase and roots function
• Use DateTime32 for getblocktemplate times
• Use typed difficulty fields rather than strings
• Move GetBlockTemplate construction into a method

Cleanups:

• Fix incorrect P2SH comments and logs
• Move get_block_template_opts to get_block_template::parameters
• Fix and simplify test imports
• Rename block_height to next_block_height
• Rename to chain_tip_and_local_time to make it clear what it contains

Review

This review is a high priority because the PR conflicts with most other RPC changes.

This PR contains a lot of code movement, it might be easier to review it using git diff --color-moved, or by reviewing each commit on GitHub.

I can do a video review after the engineering sync next week, if that would help!

Reviewer Checklist

• Will the PR name make sense to users?
  • Does it need extra CHANGELOG info? (new features, breaking changes, large changes)
• Are the PR labels correct?
• Does the code do what the ticket and PR says?
  • Does it change concurrent code, unsafe code, or consensus rules?
• How do you know it works? Does it have tests?

Follow Up Work

Actually implement long polling.

[codecov]

Codecov Report

Merging #5837 (fa8ec61) into main (68d0c55) will decrease coverage by 0.10%.
The diff coverage is 25.78%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5837      +/-   ##
==========================================
- Coverage   78.62%   78.52%   -0.11%     
==========================================
  Files         308      308              
  Lines       38605    38706     +101     
==========================================
+ Hits        30355    30393      +38     
- Misses       8250     8313      +63     

[arya2]

Thank you for the cleanup and getting rustfmt working in get_block_template_rpcs.rs again!

I left some optional comments but I'm happy with this PR as-is.

[teor2345]

Alfredo is going to review this as well.

[oxarbitrage]

https://github.com/ZcashFoundation/zebra/actions/runs/3681221203/jobs/6227680505

[oxarbitrage]

@Mergifyio update

[mergify]

Sorry but I didn't understand the command. Please consult the commands documentation 📚.

[mergify]

update

✅ Branch has been successfully updated

[teor2345]

https://github.com/ZcashFoundation/zebra/actions/runs/3681221203/jobs/6227680505

The underlying error was:

#28 pushing manifest for us-docker.pkg.dev/zealous-zebra/zebra/zebrad:main@sha256:2e7d33e1bd670fc14173ce5c782434901a29f0a87c094bce677c620c69f8374e 0.2s done
#28 ERROR: failed commit on ref "manifest-sha256:2e7d33e1bd670fc14173ce5c782434901a29f0a87c094bce677c620c69f8374e": cannot reuse body, request must be retried
------
 > exporting to image:
------

https://github.com/ZcashFoundation/zebra/actions/runs/3681221203/jobs/6227680505#step:9:410

But that link goes to PR #5839, so I think we're fine here.