Use codegen for FFI / style builder

## What problem does this solve or what need does it fill?

Bindings to languages other than Rust require a lot of repetitive type/function definitions (repeated across each set of bindings, and again in the core library).

## What solution would you like?

A custom codegen solution similar to Yoga's [enums.py](https://github.com/facebook/yoga/blob/main/enums.py) (but also covering style getters/setters) that could be used to generate (parts of) each FFI implementation, and also for implementing a style builder in the Rust API (and *maybe* also for definining the core implementations of some style enums.

## What alternative(s) have you considered?

- **Custom code for each FFI binding**. This will be hard to maintain / limit the number of language bindings we can support.
- **Using custom derives / macros to generate code**. This was initially my preferred approach but doesn't seem viable in practice due to differences in the API required by the specifics of each language (e.g. how one binds to C may be different to how ones binds to JS/WASM)
- **Generic FFI libraries like uniffi**. These seem to suffer from similar limitations to the macro approaches, and also have a limited set of languages they support, and are opinionated about how to bind to the language. They may be more viable in future.

Other solutions to solve and/or work around the problem presented.

## Additional context

- https://github.com/DioxusLabs/taffy/pull/404
- https://github.com/DioxusLabs/taffy/pull/394
- https://github.com/DioxusLabs/taffy/issues/275

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**Note: This is not blocking for releasing bindings but will likely be wanted before adding more than one or two sets of bindings.**

Start by reviewing pull requests 404 and 394 and issue 275 to understand the existing binding definitions and style APIs. Compare the repeated FFI and Rust style-builder work described there, then establish the supported generation targets and scope; done should mean an agreed codegen approach covering the required bindings and style getters/setters.

Written by the indexing model from the issue text.