[BROWSEUI][SHDOCVW] Move CExplorerBand to shdocvw (#7163)

CExplorerBand should be
implemented in shdocvw.dll.
894ad4f17d/modules/rostests/apitests/com/shdocvw.c (L37)
JIRA issue: CORE-19698
- Move CExplorerBand code
  from browseui to shdocvw.
- Delete IDS_FOLDERSLABEL
  resource string from browseui.
- Add IDS_FOLDERSLABEL
  resource string to shdocvw.
- Adapt code to these changes.
- Add sdk/include/reactos/
 shdocvw_undoc.h.
- Implement IEILIsEqual function.

sdk/include/reactos/shdocvw_undoc.h

@@ -0,0 +1,22 @@
+/*
+ * PROJECT:     ReactOS Headers
+ * LICENSE:     LGPL-2.1-or-later (https://spdx.org/licenses/LGPL-2.1-or-later)
+ * PURPOSE:     shdocvw.dll undocumented APIs
+ * COPYRIGHT:   Copyright 2024 Katayama Hirofumi MZ <katayama.hirofumi.mz@gmail.com>
+ */
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* defined(__cplusplus) */
+
+BOOL WINAPI
+IEILIsEqual(
+    _In_ LPCITEMIDLIST pidl1,
+    _In_ LPCITEMIDLIST pidl2,
+    _In_ BOOL bUnknown);
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif /* defined(__cplusplus) */