* Pick argument and return types based on opcode constraints
Co-authored-by: Jamey Sharp <jsharp@fastly.com>
* Lazily build the OPCODE_SIGNATURES list
* Skip unsupported isplit/iconcat cases
* Add an issue reference for the isplit/iconcat exemption
* Refactor the deny lists to use exceptions!, and remove redundant entries
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Co-authored-by: Jamey Sharp <jsharp@fastly.com>