Derive the import namespace from the provider module

[jeffcharles]

Description of the change

Updates the provider to have a custom section named import_namespace and has the Javy CLI use that custom section to determine what import namespace to use when creating dynamically linked modules.

Why am I making this change?

Part of #768. This change will allow plugins to specify their own import namespaces instead of having to use one set in the Javy CLI. Also arguably, javy-core should be responsible for saying when to bump any version and not the CLI.

I had a little trouble figuring out a logical place to put the derive_import_namespace_from_provider function. I'm putting it in the bytecode module for now. Arguably we could introduce an abstraction around providers with various methods for things like getting a byte slice for writing to disk, performing bytecode compilation, and getting the import namespace. I'll probably need to do that refactoring very shortly to accommodate some changes I want to make to codegen so I'm thinking it makes sense to punt until I'm working on that.

Checklist

• I've updated the relevant CHANGELOG files if necessary. Changes to javy-cli and javy-core do not require updating CHANGELOG files.
• I've updated the relevant crate versions if necessary. Versioning policy for library crates
• I've updated documentation including crate documentation if necessary.

[saulecabrera]

Is there a particular reason why this can't be import_namespace: ImportNamespace and default to FromProvider? i.e., drop the Option?

[jeffcharles]

Funnily enough that was my first implementation. Then I added back the option to bring it closer to how it's currently implemented on main. I'll drop the option and set the default to FromProvider.

[jeffcharles]

Actually, what I'll end up doing is having the provider do something polymorphically instead based on just merging #787.