Upgrade to v0.5.0 wasm3 API

[jimpo]

Addresses #24

This is a big change to support the v0.5.0 wasm3 release. I take the approach of only using the public API in wasm3.h and m3_api_wasi.h (if the wasi feature is enabled). This means I drop the following functions:

• Function::import_module_name (The name of the import module of this function)
• Module::function (Looks up a function by its index in this module)
• Runtime::find_module (Searches for a module with the given name in the runtime's loaded modules)
• Runtime::modules (Returns an iterator over the runtime's loaded modules)
• Runtime::resize_memory (Resizes the number of allocatable pages to num_pages)
• Runtime::stack and stack_mut (Returns the stack of this runtime)

Aside from this I try to keep full compatibility with the current API.

[Veykril]

Will take a look later this week(maybe tomorrow) but in general the crate was using a lot of internal things because wasm3 itself didn't really expose a nice api at the time. So getting rid of the internal dependence is definitely a plus point assuming most of the things can now be accessed via the public api.

[vshymanskyy]

@jimpo thanks for a valuable contribution!