[HSTACK] feat: added codec for DeltaScanMetaExec

[mihai-bleont]

This is mostly copied from the DeltaScanExec codec. The important difference is that DeltaScanMetaExec has no child plan, instead it has a pair vector of (file_id, row_count) embedded.

I tested with the following SQLs that used to fail:

SELECT _ACP_DATE, COUNT(*) FROM aep_dataset_next('4E9432245BC7C44B0A494037@AdobeOrg', 'prod', '', '68e0baa39036635052fa02cd') GROUP BY _ACP_DATE;
SELECT DISTINCT _ACP_DATE FROM aep_dataset_next('4E9432245BC7C44B0A494037@AdobeOrg', 'prod', '', '68e0baa39036635052fa02cd');
SELECT _ACP_DATE FROM aep_dataset_next('4E9432245BC7C44B0A494037@AdobeOrg', 'prod', '', '68e0baa39036635052fa02cd');
SELECT _ACP_DATE, COUNT(*) FROM aep_dataset_next('4E9432245BC7C44B0A494037@AdobeOrg', 'prod', '', '68e0baa39036635052fa02cd')
WHERE _ACP_DATE = '2025-10-04' GROUP BY _ACP_DATE;

[github-actions]

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