[Backport stable-25-3-1] Fix potential segfault on query termination and add metric for # of queries per pool

[ydbot]

Description

Backport of #28293 to stable-25-3-1.

[ydbot]

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin backport-28293-to-stable-25-3-1
git worktree add --checkout .worktree/backport-28293-to-stable-25-3-1 backport-28293-to-stable-25-3-1
cd .worktree/backport-28293-to-stable-25-3-1
git reset --hard HEAD^
git cherry-pick -x f29a32abb2ff2cc99d392345c9dc5bb71411f2b2
git push --force-with-lease

[github-actions]

⚪ 2025-11-10 10:31:04 UTC Pre-commit check linux-x86_64-release-asan for ab44793 has started.
⚪ 2025-11-10 10:31:19 UTC Artifacts will be uploaded here
⚪ 2025-11-10 10:34:50 UTC ya make is running...
🟡 2025-11-10 12:37:13 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?
15630	15200	0	158	256	16

🟢 2025-11-10 12:38:28 UTC Build successful.
🟢 2025-11-10 12:38:50 UTC ydbd size 3.8 GiB changed* by +20.7 KiB, which is < 100.0 KiB vs stable-25-3-1: OK

ydbd size dash	stable-25-3-1: cf28e7a	merge: ab44793	diff	diff %
ydbd size	4 053 116 848 Bytes	4 053 138 048 Bytes	+20.7 KiB	+0.001%
ydbd stripped size	1 510 616 672 Bytes	1 510 616 000 Bytes	-672 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]

⚪ 2025-11-10 10:31:34 UTC Pre-commit check linux-x86_64-relwithdebinfo for ab44793 has started.
⚪ 2025-11-10 10:31:49 UTC Artifacts will be uploaded here
⚪ 2025-11-10 10:35:36 UTC ya make is running...
🟡 2025-11-10 12:14:08 UTC Some tests failed, follow the links below. Going to retry failed tests...

Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
38296	35603	0	8	2660	25

⚪ 2025-11-10 12:17:24 UTC ya make is running... (failed tests rerun, try 2)
🟡 2025-11-10 12:36:29 UTC Some tests failed, follow the links below. Going to retry failed tests...

Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
727 (only retried tests)	702	0	2	0	23

⚪ 2025-11-10 12:36:39 UTC ya make is running... (failed tests rerun, try 3)
🟢 2025-11-10 12:52:40 UTC Tests successful.

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

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
563 (only retried tests)	545	0	0	0	18

🟢 2025-11-10 12:52:48 UTC Build successful.
🟢 2025-11-10 12:53:08 UTC ydbd size 2.3 GiB changed* by +33.1 KiB, which is < 100.0 KiB vs stable-25-3-1: OK

ydbd size dash	stable-25-3-1: cf28e7a	merge: ab44793	diff	diff %
ydbd size	2 435 738 320 Bytes	2 435 772 256 Bytes	+33.1 KiB	+0.001%
ydbd stripped size	521 620 648 Bytes	521 624 488 Bytes	+3.8 KiB	+0.001%

^{*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]

🟢 2025-11-10 10:31:53 UTC The validation of the Pull Request description is successful.

[github-actions]

⚪ 2025-11-17 11:25:49 UTC Pre-commit check linux-x86_64-release-asan for 813b5c3 has started.
⚪ 2025-11-17 11:26:05 UTC Artifacts will be uploaded here
⚪ 2025-11-17 11:29:42 UTC ya make is running...
🟡 2025-11-17 13:35:19 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?
15641	15156	0	161	307	17

🟢 2025-11-17 13:36:32 UTC Build successful.
🟢 2025-11-17 13:36:56 UTC ydbd size 3.8 GiB changed* by +20.8 KiB, which is < 100.0 KiB vs stable-25-3-1: OK

ydbd size dash	stable-25-3-1: d8b5b43	merge: 813b5c3	diff	diff %
ydbd size	4 053 962 104 Bytes	4 053 983 360 Bytes	+20.8 KiB	+0.001%
ydbd stripped size	1 510 905 120 Bytes	1 510 904 512 Bytes	-608 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]

⚪ 2025-11-17 11:26:31 UTC Pre-commit check linux-x86_64-relwithdebinfo for 813b5c3 has started.
⚪ 2025-11-17 11:26:45 UTC Artifacts will be uploaded here
⚪ 2025-11-17 11:30:22 UTC ya make is running...
🟡 2025-11-17 13:03:19 UTC Some tests failed, follow the links below. Going to retry failed tests...

Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
38319	35611	0	5	2683	20

⚪ 2025-11-17 13:06:33 UTC ya make is running... (failed tests rerun, try 2)
🟢 2025-11-17 13:21:26 UTC Tests successful.

Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
834 (only retried tests)	817	0	0	0	17

🟢 2025-11-17 13:21:36 UTC Build successful.
🟢 2025-11-17 13:21:52 UTC ydbd size 2.3 GiB changed* by +33.1 KiB, which is < 100.0 KiB vs stable-25-3-1: OK

ydbd size dash	stable-25-3-1: d8b5b43	merge: 813b5c3	diff	diff %
ydbd size	2 436 253 384 Bytes	2 436 287 264 Bytes	+33.1 KiB	+0.001%
ydbd stripped size	521 723 432 Bytes	521 727 208 Bytes	+3.7 KiB	+0.001%

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