chore: refactoring htlc expiry field related code #1281

Job	Run time
e2e test for 3-nodes-transfer --env test	4m 30s
e2e test for invoice-ops --env test	4m 10s
e2e test for open-use-close-a-channel --env test	3m 56s
e2e test for udt --env test	4m 1s
e2e test for reestablish --env test	4m 5s
e2e test for cross-chain-hub --env test	4m 32s
e2e test for router-pay --env test	4m 36s
e2e test for udt-router-pay --env test	4m 12s
e2e test for udt --env xudt-test	4m 12s
e2e test for 3-nodes-transfer --env test --env-var HASH_ALGORITHM=sha256	4m 44s
	42m 58s

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