[GWP-ASan] Rework utilities (NFC)

Few changes wrt utilities:
- split `Check` into a platform agnostic condition test and a platform
  specific termination, for which we introduce the function `die`.
- add a platform agnostic `utilities.cpp` that gets the allocation
  alignment functions original in the platform specific file, as they
  are reusable by all platforms.

Differential Revision: https://reviews.llvm.org/D89811