[fix](routineload) Honor explicit Kafka partition pins

[0AyanamiRei]

What problem does this PR solve?

Issue Number: None

Related PR: None

Problem Summary: ALTER ROUTINE LOAD with explicit Kafka partitions and offsets updated only those offsets while leaving the previous consumed partition set intact. After resume, omitted partitions could still be scheduled, and cloud progress replay could reintroduce their stale offsets. Replace the active partition state with the explicit definition and filter replayed cloud progress to that pin.

Release note

Explicit Kafka partition and offset alterations now restrict routine load consumption to the specified partitions across replay and resume.

Check List (For Author)

• Test: Unit tests added; not run as requested
• Behavior changed: Yes. Explicit Kafka partition alters now replace the consumed partition set.
• Does this need documentation: No

[hello-stephen]

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