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/Cargo.toml

@@ -22,11 +22,11 @@ thiserror = "1.0"
 libc = "0.2"
 getrandom = "0.1"
 cfg-if = "0.1.9"
-log = "0.4"
 filetime = "0.2.7"
 lazy_static = "1.4.0"
 wig = { path = "wig", version = "0.19.0" }
 wiggle = { path = "../wiggle", default-features = false, version = "0.19.0" }
+tracing = "0.1.15"
 
 [target.'cfg(unix)'.dependencies]
 yanix = { path = "yanix", version = "0.19.0" }
@@ -44,7 +44,7 @@ default = ["trace_log"]
 # This feature enables the `tracing` logs in the calls to target the `log`
 # ecosystem of backends (e.g. `env_logger`. Disable this if you want to use
 # `tracing-subscriber`.
-trace_log = [ "wiggle/tracing_log" ]
+trace_log = [ "wiggle/tracing_log", "tracing/log" ]
 # Need to make the wiggle_metadata feature available to consumers of this
 # crate if they want the snapshots to have metadata available.
 wiggle_metadata = ["wiggle/wiggle_metadata"]