scan(test): Implement scanner format round-trip tests

[teor2345]

Motivation

We skipped these tests in tickets #8019 and #8050. Now the format has settled it's a good time to do them.

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Test APIs

Proptests generate random typed data, then run it through a test closure or function. In this case, our assert_value_properties() makes sure that the round-trip format is correct.

We can't use clamp() with proptests because it sets the value to the end of the range, but we want it distributed over the range.

Solution / Testing

• Add round-trip format tests for all the scanner formats
• Add Arbitrary implementations for all the scanner formats

Related changes:

• Derive Default in test-only code to make testing easier
• Clean up an existing round-trip test

Related fixes:

• Increase proptest coverage of height serialization

(The fix for ticket #7443 in PR #7628 was incomplete.)

Review

This is a lower priority routine testing change.

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?
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[oxarbitrage]

Thanks!