fix(query): make hash join streams interruptible

[dqhl76]

I hereby agree to the terms of the CLA available at: https://docs.databend.com/dev/policies/cla/

Summary

New hash join streams could remain inside a single Processor::process() call while consuming an unbounded number of internal batches. If the query was killed during that work, the processor did not return to the scheduler to observe cancellation.

This PR:

• checks interruption between batches in join streams that can filter away or consume an unbounded number of results
• covers nested-loop scans and right-side final scans that can traverse the full build side in one call
• leaves fixed-size probe/result batch paths unchanged
• adds a stateful regression test that runs an outer left hash join, kills the query, and waits for it to leave system.processes
• refactors the existing kill test to use bounded polling instead of fixed ten-second sleeps

There are no migrations, configuration changes, or rollout steps.

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Validation:

• cargo check -p databend-query --lib
• cargo clippy -p databend-query --lib -- -D warnings
• cargo fmt --all -- --check
• python3 -m py_compile tests/suites/1_stateful/02_query/02_0000_kill_query.py
• Ruff format and lint checks for the stateful test
• Manual standalone verification through the MySQL protocol, including the outer left hash join kill regression

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

---

This change is 

AI assistance

• AI usage: An AI coding agent drafted the patch; I reviewed and added logic tests
• Responsible human: @dqhl76
• The responsible human has read every line of this diff and can explain each change

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[dqhl76]

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Codex Review: Didn't find any major issues. Breezy!

Reviewed commit: 5a98534f7d

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