Increase container registry UI page size to 20 if metadata database is enabled

Context

10 images/image tags per page on the UI is less when navigating the container registry, #364291 (comment 1908712540) & comment(internal)

@jdrpereira We had to reduce the page size due to a 1+N issue (we needed a lot of network requests for a single tag). This is no longer true on .com, but it's still the case for self-managed (those who haven't upgraded to the latest registry). We can bump it up once that is complete. I think it was 20 before. That seems a good option.

Proposal

Increase container registry page size if metadata database is enabled.

The page size can be set to 20 for both image list & the tags list pages.