--citations should report plugin citations when called on an action

[gregcaporaso]

Forum x-ref

Current behavior:

$ qiime hello-metagenome --citations
% use `qiime tools citations` on a QIIME 2 result for complete list

@misc{key0,
 author = {Caporaso, J Gregory and Bolyen, Evan},
 howpublished = {https://develop.qiime2.org},
 title = {Developing with QIIME 2},
 year = {2024}
}

$ qiime hello-metagenome duplicate-table --citations
No citations found.

Desired behavior:
The action-level --citations report should include all of the citations from the plugin-level --citations report.

[Oddant1]

@gregcaporaso I opened a PR that should close this and requested your review on it to make sure it's doing what you wanted.