wasi-common: switch all logs from log to tracing

tracing is already the dep that wiggle uses.

I used tracing structured arguments wherever I could, but I skipped over
it in all of the snapshot_0 code, because I'm going to delete that code
and replace it with wiggle-based stuff real soon.

crates/wasi-common/src/sys/osdir.rs

@@ -2,10 +2,10 @@ use super::sys_impl::oshandle::RawOsHandle;
 use super::{fd, path, AsFile};
 use crate::handle::{Handle, HandleRights};
 use crate::wasi::{types, Errno, Result};
-use log::{debug, error};
 use std::any::Any;
 use std::io;
 use std::ops::Deref;
+use tracing::{debug, error};
 
 // TODO could this be cleaned up?
 // The actual `OsDir` struct is OS-dependent, therefore we delegate