Test booru doesn't work with large Hydrus databases

[kotonbu]

As I'm sure you know, Hydrus doesn't have pagenation so it will return everything for a searched tag. From what I can tell the Test booru function searches for * which Hydrus will return every file id in the database for. When you have alot of files this takes a long time (70 seconds for my ~7 million files). I am pretty sure this is timing out and causing the Test booru to fail.

Testing using the system:limit tag instead might be a better idea but that still takes a bit of time (about 16 seconds for my database). Hydrus also has an endpoint to verify the API key at /verify_access_key that could be used.