Support AOT compiled components

[radu-matei]

ref spinframework/spin#2284
ref containerd/runwasi#405

This issue tracks support for AOT compiled components in the shim.
runwasi will support compiling the Wasm components, which will allow skipping JIT compilation every time the shim starts a new application.

[lann]

Spin will need some way for the runtime to explicitly opt-in to this and some way to pass the precompiled file (which could be the same thing as long as the latter isn't from untrusted input).

[radu-matei]

I was imagining a new OCI loader method with an explicit cwasm directory — so even if the directory was there, an implementation could choose to ignore it.

Re: untrusted input, it is the Spin shim that would compile and store the result in containerd's content store. So the content is ~as trusted as uncompiled Wasm the shim compiles today.

[jsturtevant]

fixed by #32