Support for `@unstable` features in bindings

[benbrandt]

When we've been iterating on our WIT world, it would be awesome to be able to use the new @unstable feature gate to limit breaking changes requirements to the package version while iterating on the interface.

Looking into how wit-bindgen supports this, it seems there would need to be a method of passing in these features so we can also add them to the Resolve struct creation in the parse_wit function

Questions:

1. How would you see the features being passed in?
   1. via componentize-py.toml files?
   2. via command line arguments?
   3. both?
2. Would you be ok with me attempting to tackle implementing this?

I assume that there are a few implementation details to figure out, so any input you have would be appreciated.

[dicej]

1. How would you see the features being passed in?
   
   1. via componentize-py.toml files?
   2. via command line arguments?
   3. both?

I'd say we start with command line arguments using the same syntax as wit-bindgen. We can also add componentize-py.toml support later if and when it seems useful.

2. Would you be ok with me attempting to tackle implementing this?

Sure!

I assume that there are a few implementation details to figure out, so any input you have would be appreciated.

I think it should be pretty straightforward: add the CLI arguments here and pass them along to here and here. If there's more to it than that, we'll learn about that together :)

[benbrandt]

Awesome thanks, yeah I had the same thought that matching wit-bindgen would be the way to go, and yeah I think the cli is likely enough. We can test it in our SDK wrapper and see if the toml file is also needed or not. Thanks!