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.

[rajatjindal]

Hi @jsturtevant,

#108 seems similar to this request. could you pls check and let me know if the workaround I suggested in #108 (comment) works or we need more work for this?