Generalize Trusted Book Provider so anyone can propose a TBP via a PR

### Problem

### A clear and concise description of what you want to happen

Similar to #9234, refactor the Trusted Book Provider flow so that:
* A new trusted book provider is added by opening a PR request with a yml entry for the new provider
* Minimize coding requirements for submitter: e.g. No new button template file or python class is required
* On app start, TBP's are loaded from the yml and registered with Open Library

### Additional Context
The goal is to unblock some of these [github issues](https://github.com/internetarchive/openlibrary/issues?q=is%3Aopen+is%3Aissue+label%3A%22Theme%3A+Trusted+Book+Providers%22) that propose new providers and also this [google form](https://docs.google.com/forms/d/1iqz8o7CUlkTO0nUVtu6zcUQ_aTBJRBfU46cxnMO_2A8/edit?pli=1&pli=1#responses)

### Proposal & Constraints

### What is the proposed solution / implementation?

### Is there a precedent of this approach succeeding elsewhere?

### Which suggestions or requirements should be considered for how feature needs to appear or be implemented?

### Leads

### Related files

### Stakeholders

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