FIO-9081: fixed an issue where required validation is not triggered for empty value of multiple component

[TanyaGashtold]

Link to Jira Ticket

https://formio.atlassian.net/browse/FIO-9081

Description

What changed?

Before the required validation is skipped when multiple component value is empty array. This PR add the emptyMultiValue property for required rule that force required validation for empty array.

How has this PR been tested?

Manually + test

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)
• New and existing unit/integration tests pass locally with my changes
• Any dependent changes have corresponding PRs that are listed above

[brendanbond]

This seems like an OK solution, but something seems a little off to me here. We're adding a fullValue exception to certain rules, and then an emptyMultiValue exception to that exception in certain cases. Is there any chance that we could revisit the fullValue to see if there's a better solution? @AlexeyNikipelau might be able to help here, I'll reach out to him tomorrow

[brendanbond]

closing this in favor of #130