refactor: replace manual mocks with mockall in producer

[raushan728]

Migrated manual mock implementations in producer/src/mocks.rs to mockall to address internal TODOs and standardize testing infrastructure.

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PR Summary

Low Risk
Changes are limited to test/mock infrastructure and minor syntax cleanup, with low risk to production behavior; main risk is test flakiness or compile issues under the test-helpers feature due to the new mock expectations/closures.

Overview
Refactors producer test infrastructure by replacing manual MockRelayer, MockTxPool, and MockExecutor (including FailingMockExecutor) with mockall-generated mocks behind the test-helpers feature, plus helper constructors like create_mock_relayer, create_mock_txpool, and create_failing_mock_executor to provide default behaviors.

Updates block_producer tests to use the new mock factories and removes direct construction of legacy mock structs; also includes a tiny syntax fix in produce_and_execute_predefined (missing semicolon after .into()).

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[xgreenx]

Can you please apply nightly formatting?

[raushan728]

Applied nightly formatting as requested. All imports are now in vertical layout format.

[MitchTurner]

Hey @raushan728 !

Thanks for the contribution! It's a little bit of an internal debate whether or not we should use mockall in our code. I'm of mind that we should manually write our mocks as mockall encourages users to pay too much attention to implementation details, rather than just testing external apis.

It's not up to me alone, but that's my position.

[raushan728]

Thanks @MitchTurner. I'll wait for the team's final decision on this before making further changes.

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

Unused MockRelayerLegacy re-export is dead code

Low Severity

The pub use MockRelayer as MockRelayerLegacy re-export is introduced as "backward compatibility during migration" but is never referenced anywhere in the codebase. This is dead code that adds confusion without providing any value.

 

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