[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/hostcalls/fs.rs

@@ -1,6 +1,6 @@
 #![allow(non_camel_case_types)]
 use crate::ctx::WasiCtx;
-use crate::{hostcalls_impl, wasi, wasi32};
+use crate::{wasi, wasi32};
 
 hostcalls! {
     pub unsafe fn fd_close(wasi_ctx: &mut WasiCtx, memory: &mut [u8], fd: wasi::__wasi_fd_t,) -> wasi::__wasi_errno_t;

crates/wasi-common/src/hostcalls/misc.rs

@@ -1,6 +1,6 @@
 #![allow(non_camel_case_types)]
 use crate::ctx::WasiCtx;
-use crate::{hostcalls_impl, wasi, wasi32};
+use crate::{wasi, wasi32};
 use log::trace;
 use wasi_common_cbindgen::wasi_common_cbindgen;