[Feature] Add support for global page table entries

[wipawel]

Is your feature request related to a problem? Please describe.

Certain memory areas are common for all CPUs and all contexts (e.g. kernel tasks, user tasks, etc): tmp_mfn_map, framebuffer or vga area, kernel image etc. Marking them as global has a performance benefit (although irrelevant for KTF purposes) but also help programmatically find such memory pages for page table deduplication and enables new tests.

Describe the solution you'd like
Add function enabling global entries via CR4.PGE and add a kernel cmdline parameter to control enablement of the feature.