Metarefresh module should add requested attribute values to PHP metadata when adding requested attributes

Is your feature request related to a problem? Please describe.

XML metadata supports not only specifiying an SP's requested attributes, but also specific values of those attributes:

    <RequestedAttribute FriendlyName="eduPersonEntitlement" Name="urn:oid:1.3.6.1.4.1.5923.1.1.1.7" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri" isRequired="true">                                                         
      <saml:AttributeValue xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">urn:mace:incommon:uiuc.edu:some:value</saml:AttributeValue>                                                                                                    
    </RequestedAttribute>

Currently, the metarefresh module includes the requested attributes in the generated PHP metadata, but not the requested values:

'attributes' => [
    'urn:oid:1.3.6.1.4.1.5923.1.1.1.7',
]

It should generate this instead:

'attributes' => [
    'urn:oid:1.3.6.1.4.1.5923.1.1.1.7' => [ ' urn:mace:incommon:uiuc.edu:some:value'
]

Start in the metarefresh module's RequestedAttribute parsing and PHP metadata generation entry points, using the XML example and expected PHP structure in the issue as the guide. Confirm that requested attribute values are retained and represented under their attribute names, then verify the generated metadata matches the requested shape.