Implement VFS support

[cscd98]

Might also close #553

Only tested SF II over SMB

You can ignore the build failures, this is the first time the github CI has ever been run and needs some tweaks.

[sonninnos]

I don't really have much to say since it is not relevant to my interests and expertise and testing capabilities, other than is the core option really necessary.. never seen it in any other core nor any real reason for it.

[cscd98]

I only include it because if an user has an issue with it they can disable. This is purely because MAME is huge and I can't ever test all the functionality. But I could remove it.

[sonninnos]

Hmm, let's just request it from the frontend with RETRO_ENVIRONMENT_GET_VFS_INTERFACE as usual and not force via core option.

[cscd98]

It's not forced, it requests VFS via the interface. Its just an option to disable that request. I'll remove it.

[cscd98]

Core option removed

[cscd98]

Are you happy to merge this? We will need to clear mame cache on gitlab when we do. (experience from hbmame same change)