Rework `NestedPageTable`

[not-matthias]

Instead of using the identify npt, we should allocate a dynamic npt over the system physical memory ranges.

• Add option to use dynamically allocated NPT (replace with current implementation?)
• Rename AccessType to Perm/Permission
• Add Level enum that responds to the page level that should be used.
  • If you want to allocate a NPT with huge pages, Level::1GB should be used.
  • Other levels should be: Level::2MB and Level::4KB