Publish Guava as an API dependency from plugin-api

[alejandroGM0]

Title

Publish Guava as an API dependency from plugin-api

PR description

plugin-api currently exposes Guava types in public plugin-facing signatures, but Guava was being published as an implementation/runtime dependency.

That mismatch means downstream plugin consumers can compile against the API jar, but fail as soon as they use API members such as MetricsSystem.createGuavaCacheCollector(...) or TransactionEvaluationContext.getEvaluationTimer() unless they add Guava explicitly themselves.

Solution

Publish Guava as an api dependency from plugin-api so the published metadata matches the existing public signatures.

This is the smallest safe fix because it restores compile-time consistency for downstream consumers without changing any public interfaces.

Follow-up

A medium-term cleanup could still be worthwhile: replace utility-library-specific public signatures such as Cache, Stopwatch, and possibly Pair with Besu-owned or JDK-native abstractions. That would reduce coupling in the plugin API. If maintainers think that direction is worthwhile, I can work on it as a separate follow-up.

Validation

• Regenerated the plugin-api publication metadata and confirmed Guava is now published on the compile API path.
• Verified the change does not alter any public signatures; it only aligns published dependency metadata with the existing API surface.

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• Checked out our contribution guidelines?
• Considered documentation and added the doc-change-required label if updates are required.
• Considered the changelog and included an update if required.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR aligns plugin-api’s published dependency metadata with its existing public API surface by publishing Guava as an api dependency, ensuring downstream plugin consumers can compile and use exposed Guava types without adding Guava manually.

Changes:

• Switch Guava dependency scope in plugin-api from implementation to api to match public signatures.