[SHELL32][EXPLORER][SHLWAPI][SDK] Implement SHGetSetSettings (#6982)

These settings are cached per-process (and invalidated by the global counter). This should reduce the number of registry reads performed by DefView and CFSFolder.

base/shell/explorer/trayprop.cpp

@@ -204,10 +204,9 @@ public:
 
     LRESULT OnInitDialog(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL &bHandled)
     {
-        // fix me: start menu style (classic/modern) should be read somewhere from the registry.
-        CheckDlgButton(IDC_TASKBARPROP_STARTMENUCLASSIC, BST_CHECKED); // HACK: This has to be read from registry!!!!!!!
+        BOOL modern = SHELL_GetSetting(SSF_STARTPANELON, fStartPanelOn);
+        CheckDlgButton(modern ? IDC_TASKBARPROP_STARTMENU : IDC_TASKBARPROP_STARTMENUCLASSIC, BST_CHECKED);
         _UpdateDialog();
-
         return TRUE;
     }
 
@@ -219,7 +218,9 @@ public:
 
     int OnApply()
     {
-        //TODO
+        SHELLSTATE ss;
+        ss.fStartPanelOn = !IsDlgButtonChecked(IDC_TASKBARPROP_STARTMENUCLASSIC);
+        SHGetSetSettings(&ss, SSF_STARTPANELON, TRUE);
         return PSNRET_NOERROR;
     }
 };