Kernel as a separate module

[penzn]

As discussed with @mingqiusun and @abrown another option for packaging the kernel is to package it at as a Wasm module and embedding it inside the host module as data. Not sure if this would satisfy all WIT requirements, but it definitely would make sharing between kernel and host parts of the program more explicit (as opposed to free-form memory accesses).

Open questions:

• Locating kernel function in the module, there would need to be an extra parameter for function name (requires exporting names) or function ID (requires exporting function table) or name should follow a convention of some sort.
• Data passing to and from kernel function: there is currently an API for data buffers, but it can be bypassed or simplified for CPU code, which may not work for separate modules; note this can be critical for performance

I am planning to make a quick POC for compiling multi-module code with embedding kernel module into the host module.