[GWP-ASan] Cleanup (NFC)

Cleaning up some of the GWP-ASan code base:
- lots of headers didn't have the correct file name
- adding `#ifdef` guard to `utilities.h`
- correcting an `#ifdef` guard based on actual file name
- removing an extra `;`
- clang-format'ing the code (`-style=llvm`)

Differential Revision: https://reviews.llvm.org/D89721