WebAssembly
Remove `wasm32-wasi` and `wasm32-wasi-threads` targets
These are replaced by wasm32-wasip1 and wasm32-wasip1-threads, respectively. The intention is to free up the namespace of "wasm32-wasi" for a hypothetical future target of WASI 1.0. This naming matches the Rust naming scheme which dropped support for wasm32-wasi some time ago (and renamed it to wasm32-wasip1)
This change is too early and too disruptive for downstream wasi-sdk users, many scripts still use wasm32-wasi-clang etc. It's better to revisit this after wasi 1.0 really comes out and picks up community momentum.
This change was made in Rust in April, and downstream users adjusted. The sky did not fall.
The best time to make this change was yesterday, and the second-best is now. Wasi-sdk adoption is presently at the lowest adoption it will have between now and when wasi 1.0 comes out.
Retiring the wasm32-wasi namespace well before 1.0 comes out is required to make confusion with 1.0 as low as possible when it does, by creating a long period where users of that name were were required to adjust to wasm32-wasip1 in order for their tools to keep working. Turning it off now means that by the time 1.0 comes out, no active software project will still be using the wasm32-wasi name.
