Attestation slashing protection exhaustive tests

[eserilev]

Issue Addressed

Bounded exhaustive equivalence check for the attester slashing conditions.

check_attestation contains slashing rules across five SQL queries. This test suite
restates these rules in plain Rust and compares it against the production codepaths for
every attestation history up to MAX_HISTORY attestations from epochs 0..=MAX_EPOCH.

Exhaustive tests are helpful here because the rules for check_attestation only depend
on relative attestation ordering between epochs. For example attestation histories with
epochs {5, 40, 1000} work the same as ones with epochs {0, 1, 2}. The gaps between epochs
are irrelevant, so we can stick to a small range of epochs.

These tests exist to add more coverage to the SQL itself. Our other test cases test
against the same SQL queries but for a much smaller set of inputs.

Test coverage added by this PR that doesn't currently exist in unstable:

1. SourceLessThanLowerBound and TargetLessThanOrEqLowerBound. The interchange test vectors reach them by accident after an import, but only check pass or fail. The exhaustive sweep cover both across thousands of histories.
2. No test case created an attestation that is both a double vote and a surround, or malformed with a matching target. The exhaustive tests produce every overlap.
3. Nothing on unstable checks that preliminary_check_attestation agrees with check_and_insert_attestation. The exhaustive tests do it for every attestation candidate on every history.
4. Rejected insertions in the middle of a sequence. The current tests stop at the first failure or only fail on the last item. The exhaustive tests continue after a rejection, so a later candidate is checked against a history that did not change.
5. No gaps. The exhaustive tests include all scenarios up to three stored attestations over eight epochs. The current tests only contain specific hard coded scenarios

[mergify]

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