[$] Retrieving mount and filesystem information in user space

In something of a follow-on from the mount-operation monitoring session theprevious day, Christian Brauner led another discussion about providing userspace with a mechanism to get current mount information on day two of the2023 Linux Storage, Filesystem,Memory-Management and BPF Summit. The session also continued on fromone at last year's summit-and likely others before that.There are two separate proposals for ways to retrieve this kind ofinformation, one from Miklos Szeredi and another from David Howells, bothof whom were present this year; Brauner's intent was to try to reach somekind of agreement on the way forward in the session.