Tezt/DAL: testing entrapment accusation duplicate

What

Add two integration tests for the DAL accuser.

[test_duplicate_denunciations] publishes a commitment for slot 0. The test then injects a DAL trapped attestation at level [2] and after baking [attestation_lag] blocks attempts to:

• inject a first denunciation that is expected to succeed,
• inject a second denunciation built using different shards but the same slot and the same l1 level, where each try is expected to fail:
  1. at the next block level (delegate already denounced)
  2. at the next cycle (delegate already denounced)
  3. at the next-next cycle (outdated)

[test_denunciation_next_cycle] injects two trapped attestations and inject an accusation for the first one at cycle c and another at for the second one at cycle c + 1, both injections are expected to succeed.

Why

How

Manually testing the MR

$ dune exec -- tezt/tests/main.exe  -m  'inject a denunciation at the next cycle'
$ dune exec -- tezt/tests/main.exe  -m  'inject a duplicated denunciation at different steps'

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
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