Switch page cache to approximate LRU

[cberner]

No description provided.

[adamreichold]

Two questions/remarks:

• Is keeping PrioritizedWriteCache around an artifact or is there something non-obvious of the priority mechanism left?
• Adding a rationale for switch to the commit would be nice. Most importantly what problem of the current design does this resolve?

[cberner]

It doesn't do any prioritization. It's just a wrapper around LRUCache to handle the way that cached pages are "borrowed" by the rest of the codebase.

I updated the commit

[adamreichold]

I updated the commit

Thank you! Much easier to follow for me now.