refactor(query): only call once finish callback

[sundy-li]

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Summary

fix(query): only call once finish callback of unload_spill_meta

Tests

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

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):

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This change is 

[what-the-diff]

PR Summary

• Enhancement of 'PipelineBuilder'

  The 'PipelineBuilder' has been improved to use a method known as 'take_spill_files'. This enables it to unload (or remove) specific temporary files (spill files) saved during some operations.

• Condition Check in 'main_pipeline'

  A new condition has been added in the 'main_pipeline', specifically to check for any non-empty temporary files in a remote location. This check happens before calling the unload method, hence it can prevent unnecessary operations when there are no files to remove.

• Introduction of 'take_spill_files' method in 'QueryContext'

  A new method, 'take_spill_files', has been added to 'QueryContext', tasked with retrieving these temporary files. This replaces the previous method, demonstrating a better approach to the retrieval process.

• Modification of 'unload_spill_meta'

  The method 'unload_spill_meta' has been updated to accept a list of strings representing remote temporary files. This refinement allows for more targeted unloading, increasing the efficiency of the operation.

• Code Clean up in 'mod.rs'

  A commented-out line about Python runtime initialization has been removed from the 'mod.rs' file. This change helps to clean up and maintain the tidiness of the codebase.