ldb: add "policy hints" controls to be used by password_hash module

ldb: add "policy hints" controls to be used by password_hash module

These won't have any effect yet, but soon they will allow a privileged
account to perform a password reset that respects constraints on
password history, age, and length, as if the reset was an ordinary
password change (that is, where the user provides the old password).

A normal user can't reset their own password using this, if the
organisation is using a remote service (e.g. Entra ID or Keycloak) to
manage passwords, that service can use a policy hints control to
ensure it follows AD password policy.

Entra ID Self Service Password Reset (SSPR) uses the deprecated OID.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12020

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Gary Lockyer <gary@catalyst.net.nz>