[emilioheredia-source]

Fixes #2112, which asks for a command line option to restart the menu.

Restarting the menu currently takes Exit and then starting StartMenu.exe again. From a script
that doesn't work reliably, as #2112 describes: -exit only posts MSG_EXIT to the running menu
and returns, so a StartMenu.exe started right after it often still finds the single-instance
mutex held by the exiting menu, and quits ("exit (mutex exists)"). The workaround is to wait a few
seconds and hope.

This adds StartMenu.exe -reload. Like -exit it posts MSG_EXIT to the running menu, but then it
waits for that process to end (up to 20 s) and takes the mutex, and carries on as a normal start.
It waits for the process, not only the mutex, because the old menu releases the mutex just before
it exits, and the new one should hook Explorer only once the old one is gone. If no menu is
running, -reload just starts it. If the running menu doesn't exit in time, it is left running and
-reload gives up.

The start button's right-click menu gets a Reload item that runs StartMenu.exe -reload from
the DLL's own folder. It sits above Exit and is shown and disabled under the same conditions
(EnableExit, CanShowMenu), since it exits first.

Unlike -reloadsettings, which rereads the settings from the registry, this goes through startup
anew: language files (the case in #2112), the item and icon caches in memory, and the hook into
Explorer.

Notes:

• -reloadsettings also contains -reload, so -reload counts only when no other command matched.
• The label is Menu.MenuReload, in English only for now. Other languages fall back to the
  English default until translated.
• The help (StartMenu.html) mentions Reload in the right-click menu and in the Settings section,
  and lists -reload with the other command line parameters. It no longer counts them: "supports 5"
  was already short of what StartMenu.exe accepts.

Tested on Windows 11 26H2 (26300):

• Reload from the start button's right-click menu: the menu came back, started by Explorer with
  -reload, and Explorer kept running.
• StartMenu.exe -reload 5 times in a row, each started as soon as the previous one was the
  running menu: every time the old process ended, exactly one new menu was running, and Explorer
  (same process throughout) kept running with StartMenuDLL loaded.
• StartMenu.exe -reload with no menu running: starts the menu.

Timing: a reload takes about 1.3 s, most of it the 1 s wait in ExitThreadProc. Reloading a menu
that started less than 5 s earlier takes about 6 s. That is not from -reload: RefreshInfoThread
first waits up to REFRESH_DELAY (5 s) for m_StartEvent without watching m_ExitEvent, and
shutdown waits for that thread. A plain -exit right after a start waits the same way. The startup
log shows it: the exit request at +0 ms, the DLL leaving Explorer at +6000 ms.