[BROWSEUI] Add locked toolbar state persistence (#5350)

Store the state of the explorer toolbar, locked or unlocked, in the proper
registry location and set the proper toolbar state when initialized.

CORE-9094

- Set `HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Toolbar\Locked`
to 1 when the explorer toolbar is locked, 0 when the toolbar is unlocked.
- Query `HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Toolbar\Locked`
when the toolbar is initialized to set the correct locked state.
- Set the default state of the toolbar to locked if the registry key does not
exist, matching the behavior of Windows Server 2003.

dll/win32/browseui/internettoolbar.cpp

···
 
 CInternetToolbar::CInternetToolbar()
 {
+    fLocked = SHRegGetBoolUSValueW(L"Software\\Microsoft\\Internet Explorer\\Toolbar",
+                                   L"Locked",
+                                   FALSE,
+                                   TRUE);
+
     fMainReBar = NULL;
-    fLocked = false;
     fMenuBandWindow = NULL;
     fNavigationWindow = NULL;
     fMenuCallback = new CComObject<CMenuCallback>();
···
 
     if (locked != fLocked)
     {
+        DWORD dwLocked = locked ? 1 : 0;
+        SHRegSetUSValueW(L"Software\\Microsoft\\Internet Explorer\\Toolbar",
+                         L"Locked",
+                         REG_DWORD,
+                         &dwLocked,
+                         sizeof(dwLocked),
+                         SHREGSET_FORCE_HKCU);
         fLocked = locked;
+
         rebarBandInfo.cbSize = sizeof(rebarBandInfo);
         rebarBandInfo.fMask = RBBIM_STYLE | RBBIM_LPARAM;
         bandCount = (int)SendMessage(fMainReBar, RB_GETBANDCOUNT, 0, 0);