support composing with fixed size lists

[cpetig]

This implements another part of WebAssembly/component-model#384 - needed for testing the code generation in wit-bindgen

[cpetig]

This also updates to wasm-tools 0.230.0

[cpetig]

@alexcrichton if you look for updating wasm-tools in wac this pull request includes updating to 0.230.0

[fibonacci1729]

@cpetig this LGTM; are we good to merge?

[cpetig]

Closer inspection this evening showed that encoding.rs would need special handling for fixed size lists, so I guess it is incomplete as is, sorry!

[cpetig]

But honestly I don't trust my understanding of all the code base involved until the tests in wit-bindgen come out ok, which requires more work on wit-bindgen and wasmtime.

As long as it looks good to you I assume that it could work as is.

And the tests in wit-bindgen require support by wac.

[fibonacci1729]

Sounds good. I'm happy to leave this open for awhile while the various codebases this touches solidifies a bit. Let's merge when we feel confident.

[cpetig]

If you ever need to update wasm-tools (e.g. because of the tuple bomb prevention) this patch should work well enough, I just can't tell whether it is correct enough for full fixed size list support.