feat!(nsis): add an option to customize start menu folder

[Legend-Master]

Closes #9880

[Legend-Master]

Current behavior should be

If old installer was using StartMenu/App/App.lnk and new installer uses:

• With same folder name:
  • Everything stays the same
• No additional folder or with a different folder name:
  • Nothing happens on /UPDATE
  • Create a new shortcut on manual install
  • Remove old and new shortcuts on uninstall

If old installer was using StartMenu/App.lnk and new installer uses:

• With a folder name:
  • Nothing happens on /UPDATE
  • Create a folder and new shortcut on manual install
  • Remove old and new shortcuts on uninstall
• No folder name:
  • Everything stays the same