Support Mounts into the wasm context

[jsturtevant]

Right now, youki from runwasi will take mounts from the pod spec and map them into the "container" that wraps the spin/wasmtime runtime. There may be cases, like getting a credential from a mounted file (csi secret store) that would be useful to the be exposed to the wasm runtime.

A quick look and it seems like something along the lines of loader mount files could be used.

There might be other ways to achieve this with tool like https://github.com/bytecodealliance/wasi-virt as well.