include SHA512 for output files

[artoonie]

1. Every file that's written should now use AuditableFile, instead of File. When the file writing is complete, you should call finalizeAndHash on it. That will mark it as read-only and add its hash to the audit log.
2. An exception is made for files in the Logger to avoid a circular dependency: how can you write your own hash to your file contents? In this case, we add the hash to the filename.

Alternatively, you could:

String hash;
do {
   hash = getHash(logFilePath);
   ReplaceLastLineOfFileWith("The hash of this file is %s".formatted(hash));
} while (getHash(logFilePath) != lastSeenHash)

But that will take around 10^60 years to complete by my math.

Resolves #746

[tarheel]

But that will take around 10^60 years to complete by my math.

We could make an M2 processor a requirement for running the tabulator. I bet it could complete this in more like 10^59 years.

[yezr]

I added some notes in #746 that will change the implementation of hashes

[artoonie]

Ready for review with new changes: using a .sha file instead of including the hash in the filename

[artoonie]

1. PR comments fixed
2. Changed .sha files to .hash and included hash algo in file body
3. Changed signing algo from sha256 to 512

Final review I think! @tarheel