FIO-8640: Fixes an issue where rowIndex is undefined in custom validation

[alexandraRamanenka]

Link to Jira Ticket

https://formio.atlassian.net/browse/FIO-8640

Description

The rowIndex in evelContext of custom validation was always overridden by context.index that is getting assigned only in a single place (when we have component set to multiple and process all its values at once instead of one by one)

Breaking Changes / Backwards Compatibility

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Dependencies

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Checklist:

• I have completed the above PR template
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• My changes include tests that prove my fix is effective (or that my feature works as intended)
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• Any dependent changes have corresponding PRs that are listed above