GH-123877: default to `wasm32-wasip1` instead of `wasm32-wasi` to be more specific (GH-126552)

Eventually wasm32-wasi will represent WASI 1.0, and so it's currently deprecated so it can be used for that eventual purpose. wasm32-wasip1 is also more specific to what version of WASI is currently supported.

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Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>