fix: reject block proposals in poisoned slots

[alexghr]

Reject syncing blocks with indexWithinCheckpoint > terminal block in checkpoint proposal

[AztecBot]

Flakey Tests

🤖 says: This CI run detected 3 tests that failed, but were tolerated due to a .test_patterns.yml entry.

\033FLAKED\033 (8;;http://ci.aztec-labs.com/097aeba1d6768971�097aeba1d67689718;;�):  yarn-project/end-to-end/scripts/run_test.sh simple src/e2e_p2p/sentinel_status_slash.parallel.test.ts "slashes the proposer with INACTIVITY when checkpoint validation records invalid" (205s) (code: 0) group:e2e-p2p-epoch-flakes
\033FLAKED\033 (8;;http://ci.aztec-labs.com/1d5c9bbbf8bf029f�1d5c9bbbf8bf029f8;;�): yarn-project/end-to-end/scripts/run_test.sh ha src/composed/ha/e2e_ha_full.test.ts (313s) (code: 0)
\033FLAKED\033 (8;;http://ci.aztec-labs.com/86195dad20421049�86195dad204210498;;�): yarn-project/kv-store/scripts/run_test.sh src/sqlite-opfs/internal/ordered-binary-browser.test.ts (2s) (code: 0)

[spalladino]

Should we add this to the list of slashable block proposal validation failures?