storage: remove TEST SCRIPT source

[guswynn]

These never actually became useful, and their existence is actively getting in @petrosagg and my way as we refactor stuff

Motivation

• This PR refactors existing code.

Checklist

• This PR has adequate test coverage / QA involvement has been duly considered.
• This PR has an associated up-to-date design doc, is a design doc (template), or is sufficiently small to not require a design.
• If this PR evolves an existing $T ⇔ Proto$T mapping (possibly in a backwards-incompatible way), then it is tagged with a T-proto label.
• If this PR will require changes to cloud orchestration or tests, there is a companion cloud PR to account for those changes that is tagged with the release-blocker label (example).
• This PR includes the following user-facing behavior changes:

[sploiselle]

I am unfamiliar with what prompted us to build these in the first place, but it looks like an effort you undertook so am willing to cede to your judgment that they should be yanked from the code.

[benesch]

I do love me a red diff.

[guswynn]

@benesch its my penance for #25218