Add "My Maps" sorting feature to song select

[kongehund]

In stable, when you click Edit from the main menu, you are taken to a song select screen, where starting a map will open it in the editor. Here, you can click "My Maps" to filter only your maps:

In lazer, clicking Edit from the main menu will always start the editing of a new map, so existing maps must be selected from regular song select. However, there is no "My Maps" option, so you have to manually write out "author=mapper" in the search field, which is tedious for mappers who simply want to find their own maps.

[kongehund]

#28356 relevant

[kongehund]

addressed in #18903