Text Format (%.wat) generator

The wit format is neat in that it gives hints like string to make better language bindings. However, in the process, it can be confusing what the actual imports will be. This is especially confusing as there are a couple string-based proposals to the spec. It would be nice to be able to generate`%.wat` instead and use that as the gold copy (for those who prefer seeing the raw wasm signatures). If we had this feature, it would be less scary to use the higher level types, which are becoming more interesting.