Perform redis UNLINK instead of DEL in ElasticsearchEnabledCache

What does this MR do?

We are seeing some slow DELs in the redis-cache cluster for gitlab.com. See https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/11018.

We have some DELs against a potentially quite large hash in redis. We can switch from DEL to an explicit UNLINK call similar to what was done for SetCache: !27116 (merged).

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
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• Style guides
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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

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• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
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