The `wat` crate does not support no-std

In order to build the compiler for no-std environments, none of our crates, nor their dependencies can depend on libstd, unless gated behind a Cargo feature.

Currently, we have a few dependencies on crates which do not support no-std, but which cannot be gated as they are part of the core compiler pipeline. `wat` is one of these, and is used to parse WebAssembly module/component binaries, and would be necessary to compile the outputs from `rustc` that we expect.

We'll need to figure out a solution here, I'm not sure if there is a good one, aside from trying to upstream no-std support, or forking `wat`/`wast` and implementing it ourselves.