Add error_handler hook to MultiTest

[rnemes]

Bug / Requirement Description

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Solution description

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Checklist:

• [ ] Test
• [ ] Example (both test_plan.py and .rst)
• [ ] Documentation (API)
• [ ] News fragment present for release notes
• [x] MS info leakage check
• [ ] For new driver: driver index page
• [ ] For new assertion: ui/pdf/std renderers, documentation
• [ ] For new cmdline arg: documentation