Fix Psalm-issues in the modules-directory

* Allow list of entity ids to be loaded to better support idpList

Certain metadata sources, like mdq, were don't support loading all metadata which
prevented them from being used with idplist. This change adds support for allowing
metadata sources to load a list of entities, allowing MDQ to be used for idp list.

Fixes https://github.com/simplesamlphp/simplesamlphp/issues/1135

* IDP configurable AuthnContextClassRef/AuthnContextComparison

* Add a few namespaces

Start migrating to SAML2 getters/setters

Extend @mapgrady's patch for simplesamlphp/simplesamlphp#498 to allow Scoping to be disabled on a per-idp basis as well as globally

Following up on the idea mentioned in #937: If the transport is secure fall back to the `PasswordProtectedTransport` authn context class ref, otherwise keep the current default of `Password`.

Requires a version of the SAML2 library with simplesamlphp/saml2#129 merged due to the reference on a newly defined Constant.