util/winutil: ensure domain controller address is used when retrieving remote profile information

We cannot directly pass a flat domain name into NetUserGetInfo; we must
resolve the address of a domain controller first.

This PR implements the appropriate resolution mechanisms to do that, and
also exposes a couple of new utility APIs for future needs.

Fixes #12627

Signed-off-by: Aaron Klotz <aaron@tailscale.com>

util/winutil/userprofile_windows_test.go

@@ -0,0 +1,24 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package winutil
+
+import (
+	"testing"
+
+	"golang.org/x/sys/windows"
+)
+
+func TestGetRoamingProfilePath(t *testing.T) {
+	token := windows.GetCurrentProcessToken()
+	computerName, userName, err := getComputerAndUserName(token, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := getRoamingProfilePath(t.Logf, token, computerName, userName); err != nil {
+		t.Error(err)
+	}
+
+	// TODO(aaron): Flesh out better once can run tests under domain accounts.
+}