Use ext4-DAX as the oracle for all file systems

[hayley-leblanc]

Currently the oracle file system is an instance of the same file system being tested, but it would be better for the oracle to be a more mature file system so that (non-crash-consistency) bugs in the target file system cannot obscure crash-consistency bugs.

[AbhinavMir]

Hi, would love to contribute. Is there a specific place I can start at? I have it setup now.