[scudo] Avoid splitting aligned allocations on Trusty (#69281)
Don't use multiple tagged pages at the beginning of an allocation, since
it prevents using such allocations for memrefs, and mappings aren't
reused anyway since Trusty uses MapAllocatorNoCache.
Upstreamed from https://r.android.com/2537251.
Co-authored-by: Marco Nelissen <marcone@google.com>