Rename scope constants
Rename scope constants

C libraries use SCOPE_{BASE,ONELEVEL,SUBTREE}, which has
exfiltrated into Python. C# uses Base, OneLevel and Subtree. Perl
has {base,one,sub}, as seen in the OpenLDAP command-line search
utility. The C# syntax is closest to Rust conventions, so we'll
use it.

inejge/ldap3,inejge/rust-ldap,inejge/ldap3