lsan capped AArch64 allocations at 4GB and msan at 8GB. These limits
were tied to the smaller address space of the 32-bit-style allocator.
This became possible after 8e0c1aaf6b ("[msan] Use
SizeClassAllocator64 for AArch64"), which (together with the 48-bit VMA
requirement) switched AArch64 to SizeClassAllocator64, so the limit can
now match the other 64-bit targets (1ULL << 40).
Follow-up for #89728