src: rename idmapped-mounts folder

The idmapped mounts test suite has grown to cover a lot of generic vfs
functionality that is not concerned with idmapped mounts at all.

As was discussed upstream it's time to rename it to something that
reflects its generic nature. So rename it from idmapped-mounts to vfs.

[Zorro: fix generic/689 and add it into idmapped test group]

Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Zorro Lang <zlang@kernel.org>
19 files changed