[ticket/12278] Add mcp.php core event to allow to modify modules display option

This event allows extensions to set display option for custom MCP modules
for extensions which add custom MCP modules
and some of them should be displayed conditionally.

PHPBB3-12278
Merge remote-tracking branch 'rxu3/ticket/12278' into develop

* rxu3/ticket/12278:
  [ticket/12278] Add mcp.php core event to allow to modify modules display option