[KQP RBO] Add support for aggregation with same column

[denis0x0D]

Changelog entry

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Changelog category

• Not for changelog (changelog entry is not required)

Description for reviewers

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[github-actions]

🟢 2025-11-01 15:46:04 UTC The validation of the Pull Request description is successful.

[github-actions]

⚪ 2025-11-01 15:46:14 UTC Pre-commit check linux-x86_64-release-asan for b759454 has started.
⚪ 2025-11-01 15:46:30 UTC Artifacts will be uploaded here
⚪ 2025-11-01 15:47:51 UTC ya make is running...
🟡 2025-11-01 17:41:54 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet

Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
15332	14852	0	210	249	21

🟢 2025-11-01 17:42:02 UTC Build successful.
🟡 2025-11-01 17:42:24 UTC ydbd size 3.8 GiB changed* by +235.4 KiB, which is >= 100.0 KiB vs main: Warning

ydbd size dash	main: 48dfbe5	merge: b759454	diff	diff %
ydbd size	4 068 201 464 Bytes	4 068 442 472 Bytes	+235.4 KiB	+0.006%
ydbd stripped size	1 510 269 320 Bytes	1 510 331 464 Bytes	+60.7 KiB	+0.004%

^{*please be aware that the difference is based on comparing your commit and the last completed build from the post-commit, check comparation}

[github-actions]

⚪ 2025-11-01 15:46:32 UTC Pre-commit check linux-x86_64-relwithdebinfo for b759454 has started.
⚪ 2025-11-01 15:46:49 UTC Artifacts will be uploaded here
⚪ 2025-11-01 15:48:18 UTC ya make is running...
🟡 2025-11-01 17:24:01 UTC Some tests failed, follow the links below. Going to retry failed tests...

Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
38630	35808	0	7	2792	23

⚪ 2025-11-01 17:24:14 UTC ya make is running... (failed tests rerun, try 2)
🟢 2025-11-01 17:30:35 UTC Tests successful.

Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
57 (only retried tests)	43	0	0	0	14

🟢 2025-11-01 17:30:38 UTC Build successful.
🟢 2025-11-01 17:30:53 UTC ydbd size 2.3 GiB changed* by +65.8 KiB, which is < 100.0 KiB vs main: OK

ydbd size dash	main: 88f362b	merge: b759454	diff	diff %
ydbd size	2 428 979 184 Bytes	2 429 046 600 Bytes	+65.8 KiB	+0.003%
ydbd stripped size	516 073 320 Bytes	516 087 592 Bytes	+13.9 KiB	+0.003%

^{*please be aware that the difference is based on comparing your commit and the last completed build from the post-commit, check comparation}