Move build execute prepare/user scripts to their own functions

Arran Walkerrequested to merge
ajwalker/separate-build-execute-scripts into main

What does this MR do?

Moves build execute prepare/user scripts to their own functions.

Much easier to view each commit separately.

Why was this MR needed?

Enabling an easier way to replace parts with steps execution, without too many changes.

What's the best way to test this MR?

N/A: We've just moved things.

What are the relevant issue numbers?

Edited by Arran Walker

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