[generate_ast] providing AST args, and fall back to api._codegen when output is a tuple

[HanGuo97]

This PR addresses two main points:

1. Piping AST arguments into ._codegen
2. When the host-side function returns a sequence-like output but is not TileIndexType, correctly fallback to using api._codegen

Side note, I’m not entirely sure how to handle default AST arguments. For now, I’m just using ast_params.apply_defaults(), but I’m unsure if that’s the best way.

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[jansel]

Can you fix the lints?