Add <stdbool.h> to llvm-libc-types headers that need it. (#165798)

We need `<stdbool.h>` to support having "bool" members inside pthread
structs that may get included through `<pthread.h>` from C code prior to
C23.

GitOrigin-RevId: 45b1a4bb8d0f77a336730c9da7f15820c2869611