Gmoshkin/picodata ldap auth method

Summary

• fix: used to block in net_box when failing to authenticate

• feat: ldap auth method in iproto clients

• refactor: add auth_method parameter to iproto-related interfaces

LDAP support was originally added to our tarantool fork in this MR picodata/tarantool!75

Ensure that

• New code is covered by tests
• API is documented
• Changelog is up to date
• Version is bumped in the appropriate Cargo.toml files