[Serving] Add support for input as a Batch (without model monitoring)

[tomerm-iguazio]

📝 Description

Add support for input as a batch in ModelRunnerErrorRaiser and add format_batch client function. Update body parameter type.

Important note: Batch support in model monitoring will be added in a follow-up PR and is not supported yet.

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🛠️ Changes Made

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✅ Checklist

• [x] I updated the documentation (if applicable)
• [x] I have tested the changes in this PR
• [x] I confirmed whether my changes are covered by system tests
  • [x] If yes, I ran all relevant system tests and ensured they passed before submitting this PR
  • [x] I updated existing system tests and/or added new ones if needed to cover my changes
• [x] If I introduced a deprecation:
  • [x] I followed the Deprecation Guidelines
  • [ ] I updated the relevant Jira ticket for documentation

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🧪 Testing

Add unit tests + system tests.

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🔗 References

• Ticket link: ML-11680
• Design docs links:
• External links:

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🚨 Breaking Changes?

• [ ] Yes (explain below)
• [ ] No

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🔍️ Additional Notes