eth: request id dispatcher and direct req/reply APIs (#23576)

* eth: request ID based message dispatcher

* eth: fix dispatcher cancellation, rework fetchers idleness tracker

* eth/downloader: drop peers who refuse to serve advertised chains

les/fetcher/block_fetcher_test.go

@@ -60,8 +60,8 @@ func makeChain(n int, seed byte, parent *types.Block) ([]common.Hash, map[common
 			block.AddTx(tx)
 		}
 		// If the block number is a multiple of 5, add a bonus uncle to the block
-		if i%5 == 0 {
-			block.AddUncle(&types.Header{ParentHash: block.PrevBlock(i - 1).Hash(), Number: big.NewInt(int64(i - 1))})
+		if i > 0 && i%5 == 0 {
+			block.AddUncle(&types.Header{ParentHash: block.PrevBlock(i - 2).Hash(), Number: big.NewInt(int64(i - 1))})
 		}
 	})
 	hashes := make([]common.Hash, n+1)