Add new DAL function for renaming principals

Add new DAL function for renaming principals

Previously libkadm5srv renamed principals by getting the principal
entry, renaming the entry, putting it in the DB, then deleting the old
one.  This does not work in certain KDB modules such as LDAP.  A new
DAL function is necessary to support all KDB modules.  Add a new DAL
function to support custom renames in all KDB modules, with a default
implementation that performs the previous functionality of adding and
deleting the principal entry.

NOTE: if the default rename function isn't used and iprop logging is
enabled, iprop would fail since it doesn't formally support renaming.
In that case, the call to krb5_db_rename_principal() will fail with
the code KRB5_PLUGIN_OP_NOTSUPP.

ticket: 8065