Add serialize_to_vec! convenience macro

[rozbb]

Description

Added a serialize_to_vec! macro which operates how the to_bytes! macro used to. It serializes uncompressed (fewer performance surprises that way).

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• Wrote unit tests
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[burdges]

Almost unrealted, but ark_scale::iter_ark_to_ark_bytes avoids some redundant intermediate layers. I've not upstreamed it, since I figured we cared more than anyone else, but maybe it makes sense here.