internal/wasm: Switch to wasmtime-go runtime

This commit updates the internal runtime wrapper to use wasmtime and
vendors the v0.23.0 wasmtime release and a development version
of wasmtime-go (4d860e263dc6ff070388d365c3e6b59e981df4b8). The
development version of wasmtime-go is needed to fix
https://github.com/bytecodealliance/wasmtime-go/issues/58.

Co-authored-by: Torin Sandall <torinsandall@gmail.com>
Co-authored-by: Teemu Koponen <koponen@styra.com>

Signed-off-by: Torin Sandall <torinsandall@gmail.com>