[scudo][standalone] Code tidying (NFC)

- we have clutter-reducing helpers for relaxed atomics that were barely
  used, use them everywhere we can
- clang-format everything with a recent version

Differential Revision: https://reviews.llvm.org/D90649

GitOrigin-RevId: b3420adf5a8491b4c63b54c7750fbbb6368a0a23
6 files changed