Support an emergency one-to-one split/merge in SchemeShard

[snaury]

Changelog entry

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Changelog category

• Not for changelog (changelog entry is not required)

Description for reviewers

Add a special one-to-one split/merge mode in SchemeShard to use in an emergency, e.g. when we need to garbage collect data that is not accounted by tablets but occupies storage space.

[github-actions]

⚪ 2025-04-23 17:12:40 UTC Pre-commit check linux-x86_64-relwithdebinfo for 4bac957 has started.
⚪ 2025-04-23 17:12:56 UTC Artifacts will be uploaded here
⚪ 2025-04-23 17:16:03 UTC ya make is running...
🟡 2025-04-23 19:10:35 UTC Some tests failed, follow the links below. Going to retry failed tests...

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
29472	26780	0	2	2583	107

⚪ 2025-04-23 19:13:01 UTC ya make is running... (failed tests rerun, try 2)
🟢 2025-04-23 19:28:00 UTC Tests successful.

Test history | Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
168 (only retried tests)	73	0	0	0	95

🟢 2025-04-23 19:28:07 UTC Build successful.
🟢 2025-04-23 19:28:26 UTC ydbd size 2.2 GiB changed* by +79.6 KiB, which is < 100.0 KiB vs main: OK

ydbd size dash	main: f200790	merge: 4bac957	diff	diff %
ydbd size	2 353 448 160 Bytes	2 353 529 704 Bytes	+79.6 KiB	+0.003%
ydbd stripped size	494 045 952 Bytes	494 054 752 Bytes	+8.6 KiB	+0.002%

^{*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]

⚪ 2025-04-23 17:12:41 UTC Pre-commit check linux-x86_64-release-asan for 4bac957 has started.
⚪ 2025-04-23 17:12:56 UTC Artifacts will be uploaded here
⚪ 2025-04-23 17:16:04 UTC ya make is running...
🟡 2025-04-23 19:21:29 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet Going to retry failed tests...

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
14700	14498	0	134	42	26

⚪ 2025-04-23 19:22:46 UTC ya make is running... (failed tests rerun, try 2)
🟡 2025-04-23 19:35:56 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet Going to retry failed tests...

Test history | Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
251 (only retried tests)	176	0	39	13	23

⚪ 2025-04-23 19:36:05 UTC ya make is running... (failed tests rerun, try 3)
🟡 2025-04-23 19:48:22 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet

Test history | Ya make output | Test bloat | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
99 (only retried tests)	39	0	35	2	23

🟢 2025-04-23 19:48:29 UTC Build successful.
🟡 2025-04-23 19:48:59 UTC ydbd size 3.9 GiB changed* by +131.9 KiB, which is >= 100.0 KiB vs main: Warning

ydbd size dash	main: f200790	merge: 4bac957	diff	diff %
ydbd size	4 134 291 960 Bytes	4 134 427 000 Bytes	+131.9 KiB	+0.003%
ydbd stripped size	1 431 430 968 Bytes	1 431 463 928 Bytes	+32.2 KiB	+0.002%

^{*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]

🟢 2025-04-23 18:10:03 UTC The validation of the Pull Request description is successful.