lib/nolibc: Import sys/wait.h from musl

lib/nolibc: Import sys/wait.h from musl

Import sys/wait.h from musl with minor changes:
 - Replace <bits/alltypes.h> with
   <nolibc-internal/shareddefs.h>

Source of import:
- Repository: https://git.musl-libc.org/cgit/musl
- Tag: v1.2.4 (f5f55d65)
- Path: musl/include/sys/wait.in

Checkpatch-Ignore: LOGICAL_CONTINUATIONS
Checkpatch-Ignore: FUNCTION_ARGUMENTS
Checkpatch-Ignore: LEADING_SPACE
Checkpatch-Ignore: SPACING
Signed-off-by: Michalis Pappas <michalis@unikraft.io>
Approved-by: Andrei Tatar <andrei@unikraft.io>
Reviewed-by: Andrei Tatar <andrei@unikraft.io>
Reviewed-by: Sergiu Moga <sergiu@unikraft.io>
GitHub-Closes: #1630