change(scan): Use the on-disk database for keys and results

[teor2345]

Motivation

This PR replaces the in-memory database with a database on disk.

Depends-On: #8031

Close #8019
The remaining checklist items in that ticket actually belong in other tickets.

PR Author Checklist

Check before marking the PR as ready for review:

• Will the PR name make sense to users?
• Does the PR have a priority label?
• Have you added or updated tests?
• Is the documentation up to date?

For significant changes:

• Is there a summary in the CHANGELOG?
• Can these changes be split into multiple PRs?

If a checkbox isn't relevant to the PR, mark it as done.

Specifications

The design is in ticket #8019.

Complex Code or Requirements

The "get all keys" code is a bit messy, we can fix it up after the MVP when we have a column family just for keys.

Solution

• Implement database serialization for keys and results
• Add key/birthday read and write methods
• Add scanning result read and write methods
• Spawn blocking database functions on a blocking async task

Testing

I updated the existing tests, and marked the functions that need tests with a TODO. We can do those tests in the PRs where we actually use those functions, because we might change how those functions work when we start using them.

Review

This is a routine scanner database change.

Reviewer Checklist

Check before approving the PR:

• Does the PR scope match the ticket?
• Are there enough tests to make sure it works? Do the tests cover the PR motivation?
• Are all the PR blockers dealt with?
  PR blockers can be dealt with in new tickets or PRs.

And check the PR Author checklist is complete.

Follow Up Work

• Write scanning results to database #8021

And then:

• feat(scanner): Start scanning where it left off last time #8022
• test(scan): Scan blocks containing ZECpages transactions with the ZECpages shielded key #7813

[oxarbitrage]

After i approved #8031 and it gor merged the automatic rebase into main didnt worked very well. The commits were repeated and there were conflicts. I cherry picked the relevant commits and force pushed.

[oxarbitrage]

Looks GREAT!

[oxarbitrage]

Unavailable gcloud service https://github.com/ZcashFoundation/zebra/actions/runs/7051128803/job/19193339040?pr=8036

Trying a refresh.

[oxarbitrage]

@Mergifyio refresh

[mergify]

refresh

✅ Pull request refreshed

[oxarbitrage]

Refresh didn't worked so i sent a small doc change to trigger the CI again. d216d03