Add option to preload entire PKR file to RAM

[DCxDemo]

Original design polls hdd every time game needs new data. By design, there is a queue of only 10 ram file slots. Game works with the slot index under the hood.

• load file, alloc mem, return slot index
• get ptr to mem at slot index

These days it wouldnt hurt to just load entire pkr into ram and jump instantly jump to the required data.

Can try to hook file reading and just redirect to ram stream, or can entirely rewrite high level access. It should ensure loading from hdd as a fallback too.