[gbl] Add alignment logic for EfiAllocator

Added additional prefix for buffer that allows returned pointer to be aligned.
Prefix size is stored at the end of the buffer. It is needed for deallocator
to calculate unaligned pointer value that must be used with EFI deallocate.

Bug: 361710971
Change-Id: Ied14dfeaf5f5dff948e9f10bea6b9229eb8e22f8