feat(config-cache): initial stub for cluster config cache service

[karol-kokoszka]

Fixes #3802

This is just an initial stub for new cluster-config-cache service.

General description of the goal is here https://github.com/scylladb/scylla-manager/issues/3767#issue-2208639491

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Please make sure that:

• Code is split to commits that address a single change
• Commit messages are informative
• Commit titles have module prefix
• Commit titles have issue nr. suffix

[karol-kokoszka]

@Michal-Leszczynski I'm merging it to feature branch.