Priority transactors liveness

[chrischarlesharrison]

Summary

• Replace MustGetPriorityTransactors / MustGetPriorityTransactorsForState (panic on error) with GetPriorityTransactors / GetPriorityTransactorsForState (return empty map on error) to prevent chain halts from contract failures
• Add defensive validation of contract return data: safe type conversion with panic recovery, public key length checks, all-zero key rejection, and secp256k1 curve validation via PublicKey.IsValid()
• Add unit tests for the safeConvertTransactorsMeta helper and PublicKey.IsValid() edge cases

Motivation

The old code used panic() when the priority transactors contract call failed or returned unexpected data. A panic during block processing or tx pool reset would crash the node. If the contract is misconfigured, upgraded incorrectly, or returns malformed
data, every validator would crash simultaneously — causing a full chain halt.

This PR ensures the chain stays alive by returning an empty priority transactor list (denying privileges) on any failure, and logging at Error level for operator visibility. Malformed individual entries (wrong key length, all-zero keys, keys not on the
secp256k1 curve) are skipped with Warn-level logs rather than poisoning the entire map.

Changes

• core/prioritytransactors.go — Core logic: panic removal, error-return pattern, safeConvertTransactorsMeta with panic recovery, per-entry public key validation (length, all-zero, IsValid() curve check)
• core/blockchain_reader.go — Rename MustGetPriorityTransactorsForState → GetPriorityTransactorsForState
• core/state_processor.go — Update call sites
• core/tx_pool.go — Update interface and call site
• miner/worker.go — Update call site
• core/tx_pool_test.go, miner/miner_test.go — Update mock implementations to match renamed interface
• core/prioritytransactors_test.go (new) — Unit tests for safeConvertTransactorsMeta and PublicKey.IsValid()

Test plan

• All existing tx_pool_test.go priority transaction tests pass with renamed interface
• New safeConvertTransactorsMeta tests: valid input, empty slice, nil, string/int/struct type mismatches (panic recovery)
• New PublicKey.IsValid() tests: valid key, wrong prefix (0x02), off-curve point
• Manual: verify node continues producing blocks when contract address points to invalid/empty bytecode
• Manual: verify Error/Warn log output appears when contract call fails or individual entries are malformed