Auto merge of #120468 - alexcrichton:start-wasm32-wasi-rename, r=wesleywiser

Add a new `wasm32-wasip1` target to rustc

This commit adds a new target called `wasm32-wasip1` to rustc. This new target is explained in these two MCPs:

* rust-lang/compiler-team#607
* rust-lang/compiler-team#695

In short, the previous `wasm32-wasi` target is going to be renamed to `wasm32-wasip1` to better live alongside the [new `wasm32-wasip2` target](rust-lang/rust#119616). This new target is added alongside the `wasm32-wasi` target and has the exact same definition as the previous target. This PR is effectively a rename of `wasm32-wasi` to `wasm32-wasip1`. Note, however, that as explained in rust-lang/compiler-team#695 the previous `wasm32-wasi` target is not being removed at this time. This change will reach stable Rust before even a warning about the rename will be printed. At this time this change is just the start where a new target is introduced and users can start migrating if they support only Nightly for example.

Author: bors