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/downloader/downloader_test.go

@@ -1207,8 +1207,8 @@ func checkProgress(t *testing.T, d *Downloader, stage string, want ethereum.Sync
 	t.Helper()
 
 	p := d.Progress()
-	p.KnownStates, p.PulledStates = 0, 0
-	want.KnownStates, want.PulledStates = 0, 0
+	//p.KnownStates, p.PulledStates = 0, 0
+	//want.KnownStates, want.PulledStates = 0, 0
 	if p != want {
 		t.Fatalf("%s progress mismatch:\nhave %+v\nwant %+v", stage, p, want)
 	}