Adminpack removal

Hi,

I have just tested PG17 beta1 with the E-Maj solution I maintain. The
only issue I found is the removal of the adminpack contrib.

In the emaj extension, which is the heart of the solution, and which is
written in plpgsql, the code just uses the pg_file_unlink() function to
automatically remove files produced by COPY TO statements when no rows
have been written. In some specific use cases, it avoids the user to get
a few interesting files among numerous empty files in a directory. I
have found a workaround. That's a little bit ugly, but it works. So this
is not blocking for me.

FYI, the project's repo is on github (https://github.com/dalibo/emaj),
which was supposed to be scanned to detect potential adminpack usages.

Finally, I wouldn't be surprise if some other user projects or
applications use adminpack as this is a simple way to get sql functions
that write, rename or remove files.

Regards.