* 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
e474a9e822