deps: upgrade to wasmtime@18.0.0 toolchain

[macovedj]

There have been breaking change added to wasmtime that jco hasn't started using yet. This PR does the bare minimum needed to update and preserve prior functionality. The two nontrivial updates that were added were

1.) GC instructions added to wasm-tools
2.) Support for introspection in wasmtime

For both of these, I did the simplest thing I could, frequently leaving things unimplemented, but figured that may be fine given other parts of the code.

Below are notes on how the PR currently deals with each of the needed updates

1.) Takes inspiration from similar macro blocks in wasm-tools, and occasionally relies on an unimplemented method on Translator trait. Some of the inspiration came from wasm-mutate, but there are similar macro rules in wit-component in the gc module. I'm not sure what jco's plans for GC currently are, so it's likely that I may have grabbed macro rules from the wrong place, or that some of the unimplemented methods matter, happy to look into either.

2.) This break was introduced by this PR, and I actually just reimplemented the original function with the original func signature and renamed in finish_sans_introspection, as it doesn't seem that there is a simple way to fulfill the newer signature without performing compilation steps that didn't appear to me as steps we want to port into jco, though I may be wrong. Currently the Cargo.toml points to my local branch of wasmtime, which I'll update to point at the latest release if said change gets upstreamed into wasmtime