x64: enable VTune support by default (#3821)

* x64: enable VTune support by default

After significant work in the `ittapi-rs` crate, this dependency should
build without issue on Wasmtime's supported operating systems: Windows,
Linux, and macOS. The difference in the release binary is <20KB, so this
change makes `vtune` a default build feature. This change upgrades
`ittapi-rs` to v0.2.0 and updates the documentation.

* review: add configuration for defaults in more places

* review: remove OS conditional compilation, add architecture

* review: do not default vtune feature in wasmtime-jit

crates/wasmtime/Cargo.toml

@@ -60,6 +60,7 @@ default = [
   'cranelift',
   'pooling-allocator',
   'memfd',
+  'vtune',
 ]
 
 # An on-by-default feature enabling runtime compilation of WebAssembly modules