Facility to set TransformerFactory attributes from transform:transform function

For example - you can now set attributes -

```xquery
transform:transform(
        (),
        doc("/db/csv-to-xml_v3.xsl"),
        <parameters>
                <param name="pathToCSV" value="/tmp/test.csv"/>
        </parameters>,
        <attributes>
                <attr name="http://saxon.sf.net/feature/initialTemplate" value="main"/>
        </attributes>,
        ()
)
```