Use rsix to make system calls in Wasmtime. (#3355)

* Use rsix to make system calls in Wasmtime.

`rsix` is a system call wrapper crate that we use in `wasi-common`,
which can provide the following advantages in the rest of Wasmtime:

 - It eliminates some `unsafe` blocks in Wasmtime's code. There's
   still an `unsafe` block in the library, but this way, the `unsafe`
   is factored out and clearly scoped.

 - And, it makes error handling more consistent, factoring out code for
   checking return values and `io::Error::last_os_error()`, and code that
   does `errno::set_errno(0)`.

This doesn't cover *all* system calls; `rsix` doesn't implement
signal-handling APIs, and this doesn't cover calls made through `std` or
crates like `userfaultfd`, `rand`, and `region`.

crates/wasi-common/cap-std-sync/Cargo.toml

@@ -15,18 +15,18 @@ include = ["src/**/*", "README.md", "LICENSE" ]
 wasi-common = { path = "../", version = "0.30.0" }
 async-trait = "0.1"
 anyhow = "1.0"
-cap-std = "0.19.0"
-cap-fs-ext = "0.19.0"
-cap-time-ext = "0.19.0"
-cap-rand = "0.19.0"
-fs-set-times = "0.11.0"
-system-interface = { version = "0.14.0", features = ["cap_std_impls"] }
+cap-std = "0.19.1"
+cap-fs-ext = "0.19.1"
+cap-time-ext = "0.19.1"
+cap-rand = "0.19.1"
+fs-set-times = "0.12.0"
+system-interface = { version = "0.15.0", features = ["cap_std_impls"] }
 tracing = "0.1.19"
 bitflags = "1.2"
 io-lifetimes = { version = "0.3.0", default-features = false }
 
 [target.'cfg(unix)'.dependencies]
-rsix = "0.22.4"
+rsix = "0.23.0"
 
 [target.'cfg(windows)'.dependencies]
 winapi = "0.3"