add walker and code generator to oxc-parser

[huseeiin]

to replace acorn-walk and escodegen

[Boshen]

https://github.com/oxc-project/oxc-walker hasn't been properly documented.

Given oxc-parser returns estree, I believe escodegen should also work too? I haven't tested.

[overlookmotel]

We will also add a full walker that also handles TS syntax at some point soon, once we've completed alignment of the TS AST with TS-ESLint's AST.

Codegen is more tricky. It's harder than you'd think to get AST back from JS into Rust, because you'd want to support not having to populate all fields - which doesn't have a direct mapping onto Rust's model. That will happen at some point, but not on immediate roadmap.