[wasi-common] Log string representation of WASI errno at the trace level (#760)

* Log str repr of WASI errno at trace level

This commit refactors `Error` enum, and adds logging of the WASI
errno string representation at the trace level. Now, when tracing
WASI syscalls, we will be greeted with a nicely formatted errno
value after each syscall:

```
path_open(...)
     | *fd=5
     | errno=ESUCCESS
```

This commit gets rid of `errno_from_nix`, `errno_from_win` and
`errno_from_host` helper fns in favour of direct `From` implementations
for the relevant types such as `yanix::Errno` and `winx::winerror::WinError`.
`errno_from_host` is replaced by a trait `FromRawOsError`.

* Back port changes to snapshot0

* Fix indentation in logs

crates/wasi-common/src/sys/unix/hostcalls_impl/fs.rs

@@ -175,7 +175,7 @@ pub(crate) fn path_open(
                     Errno::EMLINK if !(nix_all_oflags & OFlag::NOFOLLOW).is_empty() => {
                         return Err(Error::ELOOP);
                     }
-                    errno => return Err(host_impl::errno_from_nix(errno)),
+                    errno => return Err(errno.into()),
                 }
             } else {
                 return Err(e.into());