chore: [k218] feat(blooms): Add bloom planner and bloom builder to backend target

[grafanabot]

Backport bf60455 from #13997

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What this PR does / why we need it:

Previously, the bloom compactor component was part of the backend target in the Simple Scalable Deployment (SSD) mode. However, the bloom compactor was removed (#13969) in favour of planner and builder, and therefore also removed from the backend target.

This PR adds the planner and builder components to the backend target so it can continue building blooms if enabled.

Special notes for your reviewer:

The planner needs to be run as singleton, therefore there must only be one instance that creates tasks for the builders, even if multiple replicas of the backend target are deployed.
This is achieved by leader election through the already existing index gateway ring in the backend target. The planner leader is determined by the ownership of the leader key. Builders connect to the planner leader to pull tasks.

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
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