Change plugins_reloadPluginConfig RPC method to return the result of the reload

[fab-10]

PR description

Built on top of #9563, please review it first.

Calls to plugins_reloadPluginConfig RPC method always return success because they just trigger the reload of the plugin configuration, without waiting for the result, but this results in a bad UX for the caller, since he has no clue about the success or not of the operation, unless it looks in the logs.

Since reloading plugin configurations should be a fast operation, no more that few seconds in the worst cases, it makes sense to wait for the reloads to complete and return the result of the operations to the caller, so that if one or more reload operations fail, an error is returned, with a detailed error message, that specify which plugins have failed and the reason, and which plugin instead have reloaded their config successfully.

Fixed Issue(s)

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• Considered documentation and added the doc-change-required label to this PR if updates are required.
• Considered the changelog and included an update if required.
• For database changes (e.g. KeyValueSegmentIdentifier) considered compatibility and performed forwards and backwards compatibility tests

Locally, you can run these tests to catch failures early:

• spotless: ./gradlew spotlessApply
• unit tests: ./gradlew build
• acceptance tests: ./gradlew acceptanceTest
• integration tests: ./gradlew integrationTest
• reference tests: ./gradlew ethereum:referenceTests:referenceTests
• hive tests: Engine or other RPCs modified?

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