Document TPRParser sets chainID topology attr

[pgbarletta]

Fixes #312.

Added chainID to tpr.rst, which impacts on:

• https://userguide.mdanalysis.org/stable/formats/reference/tpr.html

And ran scripts/gen_topologyparser_attrs.py which changed a lot of things, but I just committed the line for the TPR parser and the one above (sorry, git wouldn't let me split the hunk of the 2 lines into one hunk for each line). This impacted on these files:

• https://userguide.mdanalysis.org/stable/topology_system.html#format-specific-attributes
• https://userguide.mdanalysis.org/stable/formats/index.html
• https://userguide.mdanalysis.org/stable/formats/topology.html

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:books: Documentation preview :books:: https://mdanalysis--313.org.readthedocs.build/en/313/

[pgbarletta]

As usual, I ended up overextending myself, but I think it should be ok, given that we're on the UG.