The app memory mappings for aarch64 are limited to 64GB, sometimes smaller in practice. This leads to a crash with the error message "MemorySanitizer can not mmap the shadow memory." (because an "invalid" region cannot be mapped).
This patch makes the app/shadow/origin memory mappings considerably larger, along with corresponding changes to the MEM_TO_SHADOW and SHADOW_TO_ORIGIN constants.
Note that this deprecates compatibility with 39- and 42-bit VMAs.