op-node: Mark functions test helpers

[estensen]

Description

Mark functions test helpers so filename and line number which call these functions will be reported instead of the test helpers.

[changeset-bot]

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Latest commit: 5ba3f4b

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[tynes]

This generally looks good to me, @trianglesphere and @protolambda curious of your thoughts on this

[trianglesphere]

These changes look fine. I don't think we've been super consistent about using t.Helper though.

[mslipper]

Devnet issues are related to lack of rebase. Merging.