[libc][sys/wait][linux] add missing and clean up existing macros

This patch does a few things:
- replace macro definitions with an inclusion of the linux/wait.h kernel
  header.
  - WNOHANG
  - WUNTRACED
  - WEXITED
  - WCONTINUED
  - WSTOPPED
  - P_ALL
  - P_PID
  - P_PGID
  - P_PIDFD
- Add missing macro definitions mandated by POSIX. Some are needed to build
  LLVM.
  - WCOREDUMP
  - WIFCONTINUED
  - WIFSIGNALELD
  - WIFSTOPPED
  - WSTOPSIG
- Remove glibc style __W* macros.  Users should stick with the POSIX macros. We
  can re-add them if necessary.
  - __WEXITSTATUS
  - __WTERMSIG
  - __WIFEXITED
  - __WIFSIGNALED
  - __WIFSTOPPED
  - __WIFCONTINUED
  - __WCOREDUMP
  - __W_EXITCODE
  - __W_STOPCODE
  - __W_CONTINUED
  - __WCOREFLAG

Fixes: #124944

Author: nickdesaulniers