[AMORO-4147] [Improvement]: Resource leak in CombinedDeleteFilter and MixedDeleteFilter position delete iterators.

[slfan1989]

Why are the changes needed?

Fix resource leak issues in position delete processing. CloseableIterator<Record> instances are not properly closed in CombinedDeleteFilter and MixedDeleteFilter, which can lead to:

• Memory leaks in long-running processes
• File descriptor exhaustion under heavy workloads
• Potential resource cleanup issues

Close #4147.

Brief change log

• CombinedDeleteFilter.java: Wrap CloseableIterator<Record> in try-with-resources block in positionMap initialization (line 397-410)
• MixedDeleteFilter.java: Wrap CloseableIterator<Record> in try-with-resources block in positionMap initialization (line 369-386)
• Add proper exception handling for iterator close failures in both classes

How was this patch tested?

• Add some test cases that check the changes thoroughly including negative and positive cases if possible
• Add screenshots for manual tests if appropriate
• Run test locally before making a pull request
• Existing unit tests pass successfully

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

[xxubai]

Thanks for the contribution ! @slfan1989 . LGTM

[slfan1989]

@xxubai Thank you so much for reviewing the code!