test: Use testify require/assert instead of t.Fatal/Error

[Ari1009]

Description

This PR replaces some t.fatalf instances with testify's require

Related Issue(s)

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
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• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

[vitess-bot]

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