[Enhancement]: Add/Change for multiregional metadata providers

[Vito0912]

Type of Enhancement

Server Backend and Web Interface/Frontend

Describe the Feature/Enhancement

For providers that support multiple regions, only list them once and make a dropdown or similar option to select the wanted region. This could be connected to #4085 to select multiple regions and try them one after another.

In the same change, I would propose support for multi-region functionality. This would mean that only one request is made to the provider requesting data for all the regions if a provider supports it (optimally also for custom providers).

For example, this returns the data for the book that is only available in DE and not US, but only needs one request. Providers could therefore leverage cached data and save on bandwidth and resources, providing the user higher rate limits:

https://audimeta.de/search?region=us,de&title=Hurricane%20-%20Stadt%20der%20L%C3%BCgen

Why would this be helpful?

With the growing number of custom metadata providers (especially those that support multiple regions), the selection bar is becoming increasingly large, and the need to switch between providers is also growing.

This is related to #4085.
It would also make it easier for users to select the correct regions.

Future Implementation (Screenshot)

N/A

Audiobookshelf Server Version

v2.19.5

Current Implementation (Screenshot)

No response