[msan] Increase size of app/shadow/origin mappings on aarch64

msan's app memory mappings for aarch64 are constrained by
the MEM_TO_SHADOW constant to 64GB or less, and some app
memory mappings (in kMemoryLayout) are even smaller in
practice. This will lead to a crash with the error message
"MemorySanitizer can not mmap the shadow memory" if the
executable's memory mappings (e.g., libraries) extend
beyond msan's app memory mappings.

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.

Differential Revision: https://reviews.llvm.org/D137666