all: fix warning flagging the use of DeepEqual on error (#23624)

* core: fix warning flagging the use of DeepEqual on error

* apply the same change everywhere possible

* revert change that was committed by mistake

* fix build error

* Update config.go

* revert changes to ConfigCompatError

* review feedback

Co-authored-by: Felix Lange <fjl@twurst.com>

p2p/server_test.go

@@ -370,6 +370,8 @@ func TestServerSetupConn(t *testing.T) {
 		clientkey, srvkey = newkey(), newkey()
 		clientpub         = &clientkey.PublicKey
 		srvpub            = &srvkey.PublicKey
+		fooErr            = errors.New("foo")
+		readErr           = errors.New("read error")
 	)
 	tests := []struct {
 		dontstart bool
@@ -387,10 +389,10 @@ func TestServerSetupConn(t *testing.T) {
 			wantCloseErr: errServerStopped,
 		},
 		{
-			tt:           &setupTransport{pubkey: clientpub, encHandshakeErr: errors.New("read error")},
+			tt:           &setupTransport{pubkey: clientpub, encHandshakeErr: readErr},
 			flags:        inboundConn,
 			wantCalls:    "doEncHandshake,close,",
-			wantCloseErr: errors.New("read error"),
+			wantCloseErr: readErr,
 		},
 		{
 			tt:           &setupTransport{pubkey: clientpub, phs: protoHandshake{ID: randomID().Bytes()}},
@@ -400,11 +402,11 @@ func TestServerSetupConn(t *testing.T) {
 			wantCloseErr: DiscUnexpectedIdentity,
 		},
 		{
-			tt:           &setupTransport{pubkey: clientpub, protoHandshakeErr: errors.New("foo")},
+			tt:           &setupTransport{pubkey: clientpub, protoHandshakeErr: fooErr},
 			dialDest:     enode.NewV4(clientpub, nil, 0, 0),
 			flags:        dynDialedConn,
 			wantCalls:    "doEncHandshake,doProtoHandshake,close,",
-			wantCloseErr: errors.New("foo"),
+			wantCloseErr: fooErr,
 		},
 		{
 			tt:           &setupTransport{pubkey: srvpub, phs: protoHandshake{ID: crypto.FromECDSAPub(srvpub)[1:]}},
@@ -443,7 +445,7 @@ func TestServerSetupConn(t *testing.T) {
 			}
 			p1, _ := net.Pipe()
 			srv.SetupConn(p1, test.flags, test.dialDest)
-			if !reflect.DeepEqual(test.tt.closeErr, test.wantCloseErr) {
+			if !errors.Is(test.tt.closeErr, test.wantCloseErr) {
 				t.Errorf("test %d: close error mismatch: got %q, want %q", i, test.tt.closeErr, test.wantCloseErr)
 			}
 			if test.tt.calls != test.wantCalls {