Add PubAnnotation test

[gaurav]

This PR adds a test that, given a list of either PubMed or PubMedCentral IDs, will:

1. Download the text and annotations for that document from PubAnnotation.org.
2. Run the text against Nemo-Serve.
3. Run annotations against SAPBERT, which is written into a separate track, so that both the Nemo-Serve output and the SAPBERT output can be compared.
4. Test that we get back a non-zero number of annotations from Nemo-Serve.

It also includes the produced annotations in the PubAnnotator format, which can be viewed in a PubAnnotator editor such as https://textae.pubannotation.org/editor.html?mode=edit.