Exposed extism module and added methods to get exported functions

[clarkmcc]

This PR does a couple of things:

• It exposes the extism module struct.
• It adds methods to get any exported functions from the module.
• It adds a struct to wrap the wazero function definition, allowing Extism to control the API, while also exposing some of the behaviors provided by wazero.
• It removes the module.wasm bytes from the module struct. It was unused as far as I could tell and I don't see any reason (while it's unused at least) that we wouldn't want the GC to be able to garbage collect that slice, especially when we're dealing with large modules.

[nilslice]

thank you! will review today

[clarkmcc]

🙌 Thanks for the consideration and the reviews!

[bhelx]

Thank you for taking the time @clarkmcc :)