feat(scanner): Add a very basic RAM database to store keys and scan results

[oxarbitrage]

Motivation

We want to have a database with viewing keys and scanning results. The scanner task can get the keys to scan from this database and insert results of found transactions.

This is the most basic version i was able to do with a simple test.

Should close #7904, unblock #7941 and partially unblock #7928

PR Author Checklist

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• Will the PR name make sense to users?
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Solution

Add a basic storage for the blockchain scanner project.

Testing

A new test that uses the new database was added.

Review

I am open to suggestions if we keep the PR simple, i prefer to open new tickets for more complex tasks.

Reviewer Checklist

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• 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.

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Follow Up Work

[teor2345]

This looks great!

All of my suggestions are optional, but some of them are so detailed that they belong in other tickets. So I'll go and open those tickets now. (And resolve those comments.)

[teor2345]

Thanks!