testkube: add support for defining image credentials cache ttl

[dejanzele]

Pull request description

Depends on https://github.com/kubeshop/testkube/pull/5660

Checklist (choose whats happened)

• [ ] breaking change! (describe)
• [ ] tested locally
• [ ] tested on cluster
• [ ] added new dependencies
• [ ] updated the docs
• [ ] added a test

Breaking changes

-

Changes

-

Fixes

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[rangoo94]

Optionally it could be a part of testkube-api.imageInspectionCache, as that secrets cache is used specifically for that

[ed382]

The docs code ownership here might be overkill, feel free to bypass.