(Database) Make the manual scanner have a option for the presentation/metadata match name to use the parent directory name

First and foremost consider this:

• Only RetroArch bugs should be filed here. Not core bugs or game bugs
• This is not a forum or a help section, this is strictly developer oriented

Description

Basically the title. This would be useful for manual scans where the games have a commonality, but that commonality is actually a config file, and mutable too (both by the game engine itself and by the user).

Expected behavior

Currently there is at least parts one game database in libretro-database that is (mis)using as a 'rom' config files with standardized config names (the scummvm.rdb has a awful lot of 'acsetup.cfg' from the AGS engine as 'rom'), so it would be appreciated if there was at least a option to have the standard name come not from the scanned extension but from the scanned directory name (at least for the cases where you can't change the name afaik, such as in the AGS games.).

I think DOS.rdb might have duplicates on 'non-roms' too, but that is sort of easy to work around with a conf file, which you want anyway because depending on dosbox default config to run dosgames is foolish.

This frankly adds a lot of work to the user for they to rename directories (in the case of dosbox.conf files, since it's not a native file of the game or dos, you can rename it to get the name on a manual extension scan and i think it might work already today), but it would at least allow the use of the manual scan to match a metadata in these cases where the config file is part of the engine and can't have a different name.

Actual behavior

You're kind of screwed because the automatic scanner doesn't recognize the game if you change anything in the config files, which doesn't make sense because the game engine is not even the same version and plenty of options were added or removed that you may want to use, or the user has a option they want etc. On the other hand if you try to scan for the extension (.cfg in AGS case) you're hit with hundreds or thousands of name named 'roms', while the actual name could simply be in the directory name if the user was careful to match the metadata to the directory name.

Start by tracing RetroArch's manual scanner and its metadata matching path, then compare it with the automatic scanner behavior described in the issue. Use the libretro-database entries mentioned as examples, especially scummvm.rdb and AGS config files. Done means a manual scan can optionally use each scanned directory name for presentation or metadata matching.