[hwasan] Provide aliases for c allocation functions for Fuchsia

"Interceptors" in this file aren't like the traditional interceptors
used by other sanitizers like asan. They're simply aliases to the
equivalent __sanitizer_* functions.

This also removes the WRAP(FN) declaration since it just creates
declarations for __interceptor_* functions but they seem to be unused.

Differential Revision: https://reviews.llvm.org/D145718