consensus/ethash: move remote agent logic to ethash internal (#15853)

* consensus/ethash: start remote ggoroutine to handle remote mining

* consensus/ethash: expose remote miner api

* consensus/ethash: expose submitHashrate api

* miner, ethash: push empty block to sealer without waiting execution

* consensus, internal: add getHashrate API for ethash

* consensus: add three method for consensus interface

* miner: expose consensus engine running status to miner

* eth, miner: specify etherbase when miner created

* miner: commit new work when consensus engine is started

* consensus, miner: fix some logics

* all: delete useless interfaces

* consensus: polish a bit

consensus/ethash/algorithm_test.go

@@ -730,6 +730,7 @@ func TestConcurrentDiskCacheGeneration(t *testing.T) {
 		go func(idx int) {
 			defer pend.Done()
 			ethash := New(Config{cachedir, 0, 1, "", 0, 0, ModeNormal})
+			defer ethash.Close()
 			if err := ethash.VerifySeal(nil, block.Header()); err != nil {
 				t.Errorf("proc %d: block verification failed: %v", idx, err)
 			}