tests/file-io-error: New test

tests/file-io-error: New test

This is a regression test for
https://bugzilla.redhat.com/show_bug.cgi?id=2234374.

All this test needs to do is trigger an I/O error inside of file-posix
(specifically raw_co_prw()).  One reliable way to do this without
requiring special privileges is to use a FUSE export, which allows us to
inject any error that we want, e.g. via blkdebug.

Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-Id: <20230824155345.109765-6-hreitz@redhat.com>
[hreitz: Fixed test to be skipped when there is no FUSE support, to
         suppress fusermount's allow_other warning, and to be skipped
         with $IMGOPTSSYNTAX enabled]
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>