Merge #19910: net processing: Move peer_map to PeerManager

3025ca9e77 [net processing] Add RemovePeer() (John Newbery)
a20ab22786 [net processing] Make GetPeerRef const (John Newbery)
ed7e469cee [net_processing] Move peer_map to PeerManager (John Newbery)
a529fd3e3f [net processing] Move GetNodeStateStats into PeerManager (John Newbery)

Pull request description:

  This moves `g_peer_map` from a global in net_processing.cpp's unnamed namespace to being a member `m_peer_map` of `PeerManager`.

ACKs for top commit:
  theuni:
    Re-ACK 3025ca9e77.
  dongcarl:
    Re-ACK 3025ca9
  hebasto:
    re-ACK 3025ca9e77, since my [previous](https://github.com/bitcoin/bitcoin/pull/19910#pullrequestreview-545574237) review only reverted the change that introduced NRVO in `PeerManager::GetPeerRef`, and comments are fixed in the proper commits.

Tree-SHA512: 6369eb3c688ac5b84f89f7674115f78ff02edbed76063ac2ebb1759894c9e973883e10821a35dab92bd3d738280acc095bd5368f552a060b83cd309330387d47

src/rpc/net.cpp

@@ -165,8 +165,9 @@ static RPCHelpMan getpeerinfo()
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
     NodeContext& node = EnsureNodeContext(request.context);
-    if(!node.connman)
+    if(!node.connman || !node.peerman) {
         throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
+    }
 
     std::vector<CNodeStats> vstats;
     node.connman->GetNodeStats(vstats);
@@ -176,7 +177,7 @@ static RPCHelpMan getpeerinfo()
     for (const CNodeStats& stats : vstats) {
         UniValue obj(UniValue::VOBJ);
         CNodeStateStats statestats;
-        bool fStateStats = GetNodeStateStats(stats.nodeid, statestats);
+        bool fStateStats = node.peerman->GetNodeStateStats(stats.nodeid, statestats);
         obj.pushKV("id", stats.nodeid);
         obj.pushKV("addr", stats.addrName);
         if (stats.addrBind.IsValid()) {