romio: add special-case DAOS detection logic

[roblatham00]

Pull Request Description

If users provide the 'daos:' prefix, ROMIO will use the DAOS apis directly no problem.

if users only provide a path to a file that is on daos, ROMIO's auto-detection logic will see the file system is of type "fuse", and that otherwise-unknown file system will be treated as "generic unix" (and perform pretty badly).

There appears to be no way to get FUSE to tell us what's really going on behind the scenes, so we'll look extra-hard at fuse-type files to see if it's DAOS or not.

I'm not stoked about this abstraction layering violation but I don't think there are other options. All the fs-detection magic is stuffed in this one part of ROMIO, so if we find ourselves wondering about other FUSE file systems, we can keep on adding to the logic here.

Author Checklist

• [ ] Provide Description Particularly focus on why, not what. Reference background, issues, test failures, xfail entries, etc.
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[roblatham00]

whoops i already opened a pull request for this.