FYI: v9fs/test rework

I've started picking up v9fs again for something work related, but set
out to first fix my test infrastructure.  Being lazy, I'm having
Cursor do the test infrastructure rework for me -- it is still a work
in progress, but I think it's already handling the old tests and
starting to add new ones.  I need to suck in more of the diod testing
framework as well so that I have full coverage there, and then I'm
going to look at adding hugelgupf/9p and go9p.

As part of this, I should be able to fix it for nightly builds and/or
at least tracking upstream with regression tests across the multiple
servers.

Currently running in the main branch of github.com/v9fs/test

Fortunately for everyone I'm not tilting at the caching stuff quite
yet, I'm more interested in the synthetic file system angle.  So don't
worry about me breaking everything (yet).

       -eric