[Kernel] Improvements to MmQueryStatistics

[Gliniak]

Summary

• Fixed incorrect calculation of available pages
• Changed amount of total virtual bytes
• Added real amount of reserved virtual bytes

Detailed

• total_virtual_memory_bytes was taken by some shenanigans directly from console (I taken it from one title, but it seems to be const within titles 🤔 )
• title.available_pages was probably calculated incorrectly. We forgot to remove pages used by kernel (0x300). On console they're used meanwhile in Xenia they're don't, but still we should be aware of them. (This fixes Prototype 2)

[Gliniak]

For unknown (yet) reason. This change causes our favourite wild west/horse simulator and probably some other games to flicker in certain spots, but only with resolution scaling enabled.