[wasi-common]: yanix now returns io::Error directly (#1242)

* Yanix now returns io::Error

This commit may seem somewhat controversial at first, but hear me
out first. Currently, Yanix would return a custom error that's a
wrapper around three other error types returned by various entities
inside Rust's `libstd`. In particular, Yanix's error type would wrap
`io::Error`, `num::TryFromIntError` and `ffi::NulError`. It turns
out that there is a natural conversion between the first and the last
and provided by the standard library, i.e., `From<ffi::NulError> for io::Error`
is provided. So at the surface it may seem that only the first two
wrapped error types are worth keeping.

Digging a little bit deeper into `libstd`, `num::TryFromIntError`
is essentially speaking only a marker that the integral conversion
went wrong. The struct implementing this error stores a unit type,
and nothing more. It therefore seems like a waste to wrap this
particular error when we could unify everything under `io::Error`.
And so, whenever we perform an int conversion, I suggest we simply
remap the error to `io::Error::from_raw_os_error(libc::EOVERFLOW)`
since this carries a comparable amount of information.

As a result of completely discarding `yanix::Error` custom error type,
we are invariably simplifying `yanix` itself, but also allowing
`wasi-common` to simplify in several places as well.

* Adapt wasi-common to changes in yanix

* Add Cargo.lock

* Unwrap try_into's where possible

* Remove unnecessary type annotation

crates/wasi-common/yanix/src/socket.rs

@@ -1,4 +1,5 @@
-use crate::{Error, Result};
+use crate::from_success_code;
+use std::io::Result;
 use std::os::unix::prelude::*;
 
 #[derive(Debug, Clone, Copy)]
@@ -15,7 +16,7 @@ pub unsafe fn get_socket_type(fd: RawFd) -> Result<SockType> {
     use std::mem::{self, MaybeUninit};
     let mut buffer = MaybeUninit::<SockType>::zeroed().assume_init();
     let mut out_len = mem::size_of::<SockType>() as libc::socklen_t;
-    Error::from_success_code(libc::getsockopt(
+    from_success_code(libc::getsockopt(
         fd,
         libc::SOL_SOCKET,
         libc::SO_TYPE,