The files in Tools/wasm are a little messy as nearly all Emscripten-related files are in emscripten/ while the WASI-related files are not. So I want to:

• Add a wasi/ directory and move code related to wasi.py there
• Make wasi.py a deprecated shim for calling wasi/
• Update CODEOWNERS such that @freakboy3742 isn't bothered about WASI-only stuff and I'm not bothered about Emscripten-only stuff

Linked PRs

• [3.14] GH-133600: Backport file reorg of Tools/wasm/wasi #135950