Remove `PendingSignRequests` queue from the sign module.
This closes#1027 by removing the pending sign requests queue dependency from the SendTransaction, SignMessage and Recover.
- Replace deprecated common.Hex with hexutil.Encode.
- Remove upstreamed 0010-geth-17-fix-npe-in-filter-system.patch.
- Remove upstreamed 0020-discv5-metrics.patch.
- Remove upstreamed 0026-ethdb-error-deadlock.patch.
- Update goleveldb to same version used by geth 1.8.11.
- Update PublicTransactionPoolAPI.GasPrice return type to match type in internal geth interface.
Sebastian Delgado
Adam Babik
Pedro Pombeiro
Adrià Cidre