Add native support of Observe-SDK in wasmtime runtime

[shivanshuraj1333]

As discussed over a mail thread, if someone wants to monitor their wasmplugins running inside Envoy proxy which uses Wasmtime runtime, atm observe-sdk can't be used because the runtime is the default one and we can't modify it to have the observe-sdk embedded into it.
Similar scenario happens when we use spin, since spin also uses wasmtime as wasm runtime.

One thing we can do that came out of a discussion with @nilslice is that, we can integrate observe-sdk in wasmtime and create/maintain a fork of wasmtime with builtin observe-sdk.

This issue is to track the discussion/work around this.

[nilslice]

Thank you, @shivanshu1333! We're working on this as we speak -- led by some research done by @zshipko. We'll update here soon!

[zshipko]

Hey, just wanted to drop in with an end of the week update - I'm still working on some of the changes needed for a synchronous version of the observe-sdk, I am mostly just doing a straight conversion from tokio to threads, but am getting to a point where I'm concerned about the number of threads we might be spawning so I want to get a better handle on that before moving forward.

I think I will be in a good position to start integrating with the wasmtime C api next week!

[bhelx]

Quick update here: We have a fork that modifies the Wasmtime C API to include the observe SDK, but we're still trying to figure out how to preserve the imports. The API is different enough from the rust API to cause some extra work.