On-demand partition load (synchronous)

### Task Description

**What needs to be done:**

In RLIBootstrapOperator, detect a record for a partition whose CF doesn't exist, synchronously load that partition's index from MDT into a new CF, then forward the record. Covers "late-arriving data" correctness.

**Why this task is needed:**

### Task Type

Code improvement/refactoring

### Related Issues

**Parent feature issue:** (if applicable )
**Related issues:**
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