PLAT-25512: load sphinx cache time margin config from kconf

[yossipapi]

Pull Request Checklist

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General notes -

• [ ] I have tested the changes locally.
• [ ] I have written unit tests where applicable.
• [ ] I have updated documentation where needed.
• [ ] I have added comments to complex code.
• [ ] This PR follows the coding style guidelines.
• [ ] I have updated release notes with new feature

New Kaltura Types

• [ ] I have created new clients
• [ ] I have notified related apps - KMCNG / KMS / EP .... about new clients

New Kaltura Services / Actions

• [ ] I have added a deployment script

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1. What is the purpose of this PR?

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2. Does this change affect production code or infrastructure?

   • [ ] Yes
   • [ ] No

3. If yes, what is the rollback plan?

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