Add runner_controller_tokens table and model

What does this MR do and why?

This MR adds runner_controller_tokens table and model as a part of Runner controller management API (Part 2) Runne... (#578797 - closed).

runner_controller_tokens belongs to runner_controllers table that was introduced by Add runner controller management API (!210821 - merged).

References

• Part of Runner controller management API (Part 2) Runne... (#578797 - closed).
• Part of the epic: Phase 1: admission control (&19660).

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