Is there a tool somewhere that can do this?
In the IDE you add a certain service to your app. In the newer library versions you can click on the blue version number. The web page with information will then be displayed in your browser. It is then often indicated that any (open source) libraries are used.
And do I have to provide an open source library list to the app?
Mmm. A bit unclear because Google talks about a privacy statement in the huge mountain of documents. Also in this forum are a number of posts in which an update of or a completely new app was hit with a rejection because they had just given the wrong answer to Google's questions.
It is still unclear to me whether Google is already comparing the answers given in the first review with the de-compiled program version or only after a protest against the rejection of the (update) of the app.
The introduction of new rules goes a bit further step by step. Complying with all kinds of privacy rules afterwards is a "hell-of-a-job". I would still recommend "Privacy-by-design" for new programs.