* 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
c183e93b80