refactor(core): merge invoke items into single struct, allow ?

[chippers]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• New Binding Issue #___
• Code style update
• Refactor
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Does this PR introduce a breaking change? (check one)

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• No (no release since the breaking change that this refactors)

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Other information:
Not sure if InvokeError and InvokeResponse is the final abstraction to use - but we can finalize that after we get command returns using a trait. I undid most of the InvokeResponse interface changes so that we can use ? inside of the closures. I added InvokeError to have an easy to use error type for it and CommandArg. We still convert to an InvokeResponse before formatting the callback so that we can parse the value into a json error instead of failing parsing altogether