Add limit for ISR cache files written to disk

[hdodov]

Goals

1. Avoid filling up the server disk and grinding it to a halt

Non-Goals

No response

Background

There's the cacheMaxMemorySize option, but it limits only the in-memory cache, not the cache files written to disk.

Proposal

I have a typical standalone Docker setup with Next 15 and the issue I'm having is that my servers eventually start running out of disk space due to the ISR cache, i.e. the files in .next/server/app inside the container.

To fix this, I have to manually delete files from there and free up space as needed, which is tough to do efficiently. It would be ideal if Next provided a limit for the files written to disk (similar to cacheMaxMemorySize), which evicts entries in LRU fashion.