* Fix world save rename not applying new name
KeyboardCompleteWorldNameCallback had no _WINDOWS64 branch, so the
typed name was validated then silently discarded on every rename attempt.
Write the new name to a worldname.txt sidecar file next to the save
(Windows64\GameHDD\{folder}\worldname.txt) and update the in-memory
display name immediately. ReadLevelNameFromSaveFile now checks for this
sidecar first so renamed saves persist correctly across restarts.
* Fixed gamertag being blank upon renaming and re-joining a save
* Save deletion fix, exiting without saving fix
* Add native in-game keyboard UI for world naming and renaming
