[FR] Add "Recent Sessions" top-level submenu to File menu

Description of the Issue

The File menu offers a means for saving and loading a session (to/from a file), and sessions can be loaded via command line argument, but there is no easy method for easily reloading a recently chosen session.

This feature request proposes a Recent Sessions entry on the File menu. It would be the top-level of a submenu that would open to reveal the most-recently-used session files.

Some points:

• Most recent session files would be listed at the top of the submenu, oldest used at the bottom
• Choosing a session from the submenu would offer to save the current session, then would close all file tabs and load from the chosen session file
• There would obviously need to be a limit of the number of items possible to show in the submenu
• There would be no need to show the currently loaded session file in the menu (like the recent-files-history doesn't show currently files in its list)

Debug Information

Comments above based on feature content present in N++ 8.4.9.

Start by locating the existing File menu commands for saving and loading sessions, then trace how command-line session loading and recent-file history are handled. Define the recent-session ordering, item limit, current-session exclusion, save prompt, tab closure, and loading behavior before implementing and testing the menu flow.