Union with conflicting metadata fails as logical/physical stages merge it differently #26880

Describe the bug

When union fields have metadata, the physical and logical layer merge them in different ways, which might result in different schemas.

To Reproduce

SELECT with_metadata(1, 'id', '1') UNION SELECT with_metadata(NULL, 'id', '2');

returns:

Internal error: Physical input schema should be the same as the one converted from logical input schema. Differences:
	- field metadata at index 0 [with_metadata(Int64(1),Utf8("id"),Utf8("1"))]: (physical) {"id": "1"} vs (logical) {"id": "2"}.

Expected behavior

field metadata merging should be uniform and return the expected results.

Additional context

No response

Willingness to contribute

None