test-refactor: do not overspecify read operations order or number

[LGLO]

Description

Step 1 of files operations overspecification clean-up. It is simple, because this is about reads only. We should not care about when something is read or how many times. Mock files are setup in tests and updated by write operations. Nothing else matters.

Checklist

• Commit sequence broadly makes sense and commits have useful messages.
• New tests are added if needed and existing tests are updated.
• Relevant logging and metrics added
• CI passes. See note on CI.
• Any changes are noted in the changelog.md for affected crate
• Self-reviewed the diff

Note on CI

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You will need to get someone with write privileges. Please contact IOG Partner Chains developers to do this
for you.