test(e2e): stabilize invalid proposal slashing target slot in attested_invalid_proposal

[spalladino]

Summary

• skip target slots in attested invalid proposal slashing when the previous pipelined target slot has the same bad proposer
• log the previous pipelined target proposer while selecting the test slot

Why

CI run http://ci.aztec-labs.com/bf99262466eae1dd selected slot 21 for the invalid checkpoint scenario, but the same bad proposer could first run a prior pipelined slot and build only a partial checkpoint. That left the test waiting for block-proposed events on the intended slot that never arrived. Requiring the previous pipelined target slot to have a different proposer keeps the malicious config from being consumed by the wrong slot after the epoch warp.

Testing

• yarn format end-to-end
• yarn build
• LOG_LEVEL='info; debug:sequencer,publisher,validator' yarn workspace @aztec/end-to-end test:e2e e2e_slashing/attested_invalid_proposal.test.ts