[wasm-split] Do not split out functions referring to segments

[tlively]

Since data and elem segments cannot be imported or exported, there is no way to
access them from the secondary module, so functions that need to refer to them
cannot be split out.

Fixes #6512.

[tlively]

• [wasm-split] Do not split out functions referring to segments #6517 👈
• main

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[kripken]

Another option might be to export from the primary module methods that do a drop etc., and call those from the secondary module. If these operations are common we might want to do that, but I'm not sure if they are?

[tlively]

That's a good idea, too. Another possibility I thought of was to do an analysis to see if the segment could be moved (rather than copied) to the secondary module. I think these instructions are rare so far, so it's not worth doing anything complicated, but if e.g. array.new_data becomes common at some point, it might be worth improving this. I'll add a TODO.