25-3: make storage balancer async

[vporyadke]

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]

🟢 2025-11-21 16:55:32 UTC The validation of the Pull Request description is successful.

[github-actions]

⚪ 2025-11-21 16:46:06 UTC Pre-commit check linux-x86_64-release-asan for 718a033 has started.
⚪ 2025-11-21 16:46:21 UTC Artifacts will be uploaded here
⚪ 2025-11-21 16:49:59 UTC ya make is running...
🟡 2025-11-21 18:56:12 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?
15787	15298	0	206	263	20

🟢 2025-11-21 18:57:31 UTC Build successful.
🟢 2025-11-21 18:57:55 UTC ydbd size 3.8 GiB changed* by +160 Bytes, which is < 100.0 KiB vs stable-25-3: OK

ydbd size dash	stable-25-3: 4f820ef	merge: 718a033	diff	diff %
ydbd size	4 063 815 896 Bytes	4 063 816 056 Bytes	+160 Bytes	+0.000%
ydbd stripped size	1 514 221 632 Bytes	1 514 221 696 Bytes	+64 Bytes	+0.000%

^{*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]

⚪ 2025-11-24 10:41:13 UTC Pre-commit check linux-x86_64-relwithdebinfo for 718a033 has started.
⚪ 2025-11-24 10:41:28 UTC Artifacts will be uploaded here
⚪ 2025-11-24 10:45:04 UTC ya make is running...
🟡 2025-11-24 12:13:04 UTC Some tests failed, follow the links below. Going to retry failed tests...

Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
38649	35976	0	5	2650	18

⚪ 2025-11-24 12:16:13 UTC ya make is running... (failed tests rerun, try 2)
🟢 2025-11-24 12:33:22 UTC Tests successful.

Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
553 (only retried tests)	536	0	0	0	17

🟢 2025-11-24 12:33:30 UTC Build successful.
🟢 2025-11-24 12:33:48 UTC ydbd size 2.3 GiB changed* by +96 Bytes, which is < 100.0 KiB vs stable-25-3: OK

ydbd size dash	stable-25-3: 4f820ef	merge: 718a033	diff	diff %
ydbd size	2 441 572 656 Bytes	2 441 572 752 Bytes	+96 Bytes	+0.000%
ydbd stripped size	522 613 000 Bytes	522 613 000 Bytes	0 Bytes	0.000%

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