Increase the default lock-stripe factor for PagedFiles

This reduces the lock contention on concurrent page faulting.
Load testing in realistic scenarios have shown that 256 locks are too few, and that 1024 is a lot better.
This increases the memory pressure that each mapped file puts on the system, so to counter this, the initial size of each map in the translation tables have been reduced from 32 to 8.
Merge pull request #3448 from chrisvest/2.2-pagecache-stripe

Increase the default lock-stripe factor for PagedFiles