Avoid unexpected CRIT errors when resubscribing to mediator buckets

[snaury]

Changelog entry

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Changelog category

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Description for reviewers

It was discovered that mediator timecast logged unexpected CRIT errors due to erroneously processing bucket updates as synchronized, when in fact they are not. This didn't produce any noticeable problems except complaining about unexpected updates.

Fixes #14794.

[github-actions]

🟢 2025-02-19 14:26:47 UTC The validation of the Pull Request description is successful.

[github-actions]

⚪ 2025-02-19 14:26:33 UTC Pre-commit check linux-x86_64-release-asan for 26d21c4 has started.
⚪ 2025-02-19 14:26:48 UTC Artifacts will be uploaded here
⚪ 2025-02-19 14:29:46 UTC ya make is running...
🟡 2025-02-19 15:55:39 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?
11736	11475	0	209	16	36

⚪ 2025-02-19 15:57:10 UTC ya make is running... (failed tests rerun, try 2)
🟢 2025-02-19 16:15:09 UTC Tests successful.

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

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
315 (only retried tests)	277	0	0	4	34

🟢 2025-02-19 16:15:19 UTC Build successful.
🟢 2025-02-19 16:15:47 UTC ydbd size 3.6 GiB changed* by -48 Bytes, which is <= 0 Bytes vs main: OK

ydbd size dash	main: 02fadfa	merge: 26d21c4	diff	diff %
ydbd size	3 894 661 032 Bytes	3 894 660 984 Bytes	-48 Bytes	-0.000%
ydbd stripped size	1 363 540 128 Bytes	1 363 540 128 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}

[github-actions]

⚪ 2025-02-19 14:27:37 UTC Pre-commit check linux-x86_64-relwithdebinfo for 26d21c4 has started.
⚪ 2025-02-19 14:27:59 UTC Artifacts will be uploaded here
⚪ 2025-02-19 14:30:47 UTC ya make is running...
🟡 2025-02-19 15:23:02 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?
19048	17698	0	1	1215	134

⚪ 2025-02-19 15:25:19 UTC ya make is running... (failed tests rerun, try 2)
🟢 2025-02-19 15:49:27 UTC Tests successful.

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

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
202 (only retried tests)	73	0	0	1	128

🟢 2025-02-19 15:49:36 UTC Build successful.
🟢 2025-02-19 15:49:54 UTC ydbd size 2.1 GiB changed* by 0 Bytes, which is <= 0 Bytes vs main: OK

ydbd size dash	main: 02fadfa	merge: 26d21c4	diff	diff %
ydbd size	2 238 945 296 Bytes	2 238 945 296 Bytes	0 Bytes	0.000%
ydbd stripped size	474 411 320 Bytes	474 411 320 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}