executor: Fix for dynamic partition pruning and union_scan

[mjonss]

What problem does this PR solve?

Issue Number: close #29851 (reverting #26876 + fix for union scan with transaction buffer)

Problem Summary:

What is changed and how it works?

WIP, mostly a prototype for understanding the real issue.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

None

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[mjonss]

Replaced by #31634