p2p: new dial scheduler (#20592)

* p2p: new dial scheduler

This change replaces the peer-to-peer dial scheduler with a new and
improved implementation. The new code is better than the previous
implementation in two key aspects:

- The time between discovery of a node and dialing that node is
  significantly lower in the new version. The old dialState kept
  a buffer of nodes and launched a task to refill it whenever the buffer
  became empty. This worked well with the discovery interface we used to
  have, but doesn't really work with the new iterator-based discovery
  API.

- Selection of static dial candidates (created by Server.AddPeer or
  through static-nodes.json) performs much better for large amounts of
  static peers. Connections to static nodes are now limited like dynanic
  dials and can no longer overstep MaxPeers or the dial ratio.

* p2p/simulations/adapters: adapt to new NodeDialer interface

* p2p: re-add check for self in checkDial

* p2p: remove peersetCh

* p2p: allow static dials when discovery is disabled

* p2p: add test for dialScheduler.removeStatic

* p2p: remove blank line

* p2p: fix documentation of maxDialPeers

* p2p: change "ok" to "added" in static node log

* p2p: improve dialTask docs

Also increase log level for "Can't resolve node"

* p2p: ensure dial resolver is truly nil without discovery

* p2p: add "looking for peers" log message

* p2p: clean up Server.run comments

* p2p: fix maxDialedConns for maxpeers < dialRatio

Always allocate at least one dial slot unless dialing is disabled using
NoDial or MaxPeers == 0. Most importantly, this fixes MaxPeers == 1 to
dedicate the sole slot to dialing instead of listening.

* p2p: fix RemovePeer to disconnect the peer again

Also make RemovePeer synchronous and add a test.

* p2p: remove "Connection set up" log message

* p2p: clean up connection logging

We previously logged outgoing connection failures up to three times.

- in SetupConn() as "Setting up connection failed addr=..."
- in setupConn() with an error-specific message and "id=... addr=..."
- in dial() as "Dial error task=..."

This commit ensures a single log message is emitted per failure and adds
"id=... addr=... conn=..." everywhere (id= omitted when the ID isn't
known yet).

Also avoid printing a log message when a static dial fails but can't be
resolved because discv4 is disabled. The light client hit this case all
the time, increasing the message count to four lines per failed
connection.

* p2p: document that RemovePeer blocks

p2p/util_test.go

@@ -19,30 +19,32 @@ package p2p
 import (
 	"testing"
 	"time"
+
+	"github.com/ethereum/go-ethereum/common/mclock"
 )
 
 func TestExpHeap(t *testing.T) {
 	var h expHeap
 
 	var (
-		basetime = time.Unix(4000, 0)
+		basetime = mclock.AbsTime(10)
 		exptimeA = basetime.Add(2 * time.Second)
 		exptimeB = basetime.Add(3 * time.Second)
 		exptimeC = basetime.Add(4 * time.Second)
 	)
-	h.add("a", exptimeA)
 	h.add("b", exptimeB)
+	h.add("a", exptimeA)
 	h.add("c", exptimeC)
 
-	if !h.nextExpiry().Equal(exptimeA) {
+	if h.nextExpiry() != exptimeA {
 		t.Fatal("wrong nextExpiry")
 	}
 	if !h.contains("a") || !h.contains("b") || !h.contains("c") {
 		t.Fatal("heap doesn't contain all live items")
 	}
 
-	h.expire(exptimeA.Add(1))
-	if !h.nextExpiry().Equal(exptimeB) {
+	h.expire(exptimeA.Add(1), nil)
+	if h.nextExpiry() != exptimeB {
 		t.Fatal("wrong nextExpiry")
 	}
 	if h.contains("a") {