Retry async verifier when slowHashAsync returns unknown result

[MoneroOcean]

Motivation

• Some verifier implementations return an unknown/temporary result (e.g. false) which should trigger a retry instead of immediately failing verification.

Description

• Add retry logic for asynchronous share verification in verifySlowShare that retries when global.coinFuncs.slowHashAsync calls back with false, using configurable limits and delays via global.config.pool.verifyShareRetry.
• Introduce helper getters getVerifyRetryLimit() and getVerifyRetryDelayMs() with safe defaults of 3 retries and 30 ms delay and robust parsing of the config values.
• Preserve original behavior for null results and mismatched hashes while capping computed delays and retries to sane integer values.
• Add a unit test submit retries async verifier when verifier result is unknown in tests/pool/validation/core.js that simulates slowHashAsync returning false a few times before returning a valid result and asserts the retry behavior.

Testing

• Ran the pool validation tests in tests/pool/validation/core.js including the new retry test which asserts slowHashAsync was invoked the expected number of times and that the submission succeeded; the tests passed.
• Existing async verification behavior for null results and hash mismatches was exercised by the same test suite and remained unchanged.

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Codex Task