New API: xfs_info2

Reimplement xfs_info by returning a hash table of values (rather than
a limited struct), and by writing it in OCaml with PCRE which makes
string parsing a lot simpler.  This will now flexibly return all the
fields from the underlying xfs_info command, even (hopefully) future
fields.

Note the field values are returned as strings, because the actual
fields in xfs_info output are fairly random and free-form.  There is a
trade off here between returning as much information as we can, and
requiring the user to do a bit of (simple) field parsing.

Fixes: https://issues.redhat.com/browse/RHEL-143673

generator/proc_nr.ml

@@ -524,6 +524,7 @@ let proc_nr = [
 519, "setfiles";
 520, "ntfs_chmod";
 521, "inspect_get_windows_group_policy";
+522, "xfs_info2";
 ]
 
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