Move wai-bindgen-wasmer to Wasmer repo

[theduke]

The wai-bindgen-wasmer runtime utility crate has dependencies on Wasmer, which makes using WAI inside the Wasmer code base extremely diffcult and awkard.

The short term plan is to move the crate to the Wasmer repo.

In the medium term we want to rewrite wai-bindgen-gen-wasmer to make this crate redundant.