consensus, core, ethstats: use engine specific block beneficiary (#14318)

* consensus, core, ethstats: use engine specific block beneficiary

* core, eth, les, miner: use explicit beneficiary during mining

consensus/consensus.go

@@ -49,6 +49,11 @@ type ChainReader interface {
 
 // Engine is an algorithm agnostic consensus engine.
 type Engine interface {
+	// Author retrieves the Ethereum address of the account that minted the given
+	// block, which may be different from the header's coinbase if a consensus
+	// engine is based on signatures.
+	Author(header *types.Header) (common.Address, error)
+
 	// VerifyHeader checks whether a header conforms to the consensus rules of a
 	// given engine. Verifying the seal may be done optionally here, or explicitly
 	// via the VerifySeal method.