[PoC] Change the default pagesize on aarch64 from 4k to 16k to support apple hardware

[kit-ty-kate]

This is an attempt at hotfixing #529 for 16k aarch64 hardware as I need to have a working solo5 to test mirage/ocaml-solo5#122 on my work laptop (apple M1 hardware).

I don't think this should be merged as-is as I think sysconf(_SC_PAGESIZE) should be used instead but the goal is to show which parts of the code needs to change for solo5 to work on 16k pagesize hardware.

As of afa7fdf: only solo5-spt works. solo5-hvt infinit loops for some reason, so something else might be needed.

[TImada]

For solo5-hvt, modification of aarch64_setup_memory_mapping [1] and TCR_TG_FLAGS [2] will be needed at least.

The current implementation creates a page table having mixed 1GB/2MB/4KB blocks. However, a page table having mixed 32MB/16KB blocks needs to be created to support Apple hardware.
(Check [3] for details)

In addition, TG0 and TG1 bits of TCR_EL1 needs to be configured to use the 16KB granule size.
(Check [4] for details)

[1] https://github.com/Solo5/solo5/blob/master/tenders/hvt/hvt_cpu_aarch64.c#L38
[2] https://github.com/Solo5/solo5/blob/master/tenders/hvt/hvt_kvm_aarch64.c#L131
[3] https://developer.arm.com/documentation/den0024/a/The-Memory-Management-Unit/Translation-tables-in-ARMv8-A/Effect-of-granule-sizes-on-translation-tables
[4] https://developer.arm.com/documentation/ddi0595/2020-12/AArch64-Registers/TCR-EL1--Translation-Control-Register--EL1-

16KB page size support requires slightly complicated work. 😢