Move realization of pool stats collector to cpp files

[kruall]

Changelog entry

Changelog category

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Description for reviewers

...

[github-actions]

🟢 2025-03-10 10:07:28 UTC The validation of the Pull Request description is successful.

[github-actions]

⚪ 2025-03-10 10:08:13 UTC Pre-commit check linux-x86_64-release-asan for e48ad20 has started.
⚪ 2025-03-10 10:08:27 UTC Artifacts will be uploaded here
⚪ 2025-03-10 10:11:12 UTC ya make is running...
🟡 2025-03-10 11:29:43 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?
13624	13425	0	150	13	36

⚪ 2025-03-10 11:31:07 UTC ya make is running... (failed tests rerun, try 2)
🟡 2025-03-10 11:53:45 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?
300 (only retried tests)	180	0	82	4	34

⚪ 2025-03-10 11:53:59 UTC ya make is running... (failed tests rerun, try 3)
🟡 2025-03-10 12:11:46 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?
200 (only retried tests)	113	0	52	2	33

🟢 2025-03-10 12:11:56 UTC Build successful.
🟢 2025-03-10 12:12:27 UTC ydbd size 3.7 GiB changed* by -1.3 MiB, which is <= 0 Bytes vs main: OK

ydbd size dash	main: afdf947	merge: e48ad20	diff	diff %
ydbd size	3 996 379 320 Bytes	3 994 971 424 Bytes	-1.3 MiB	-0.035%
ydbd stripped size	1 389 073 736 Bytes	1 388 598 664 Bytes	-463.9 KiB	-0.034%

^{*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]

⚪ 2025-03-10 10:08:27 UTC Pre-commit check linux-x86_64-relwithdebinfo for e48ad20 has started.
⚪ 2025-03-10 10:08:42 UTC Artifacts will be uploaded here
⚪ 2025-03-10 10:11:31 UTC ya make is running...
🟡 2025-03-10 11:21:23 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?
28094	25507	0	2	2467	118

⚪ 2025-03-10 11:24:33 UTC ya make is running... (failed tests rerun, try 2)
🟡 2025-03-10 11:41:32 UTC Some tests failed, follow the links below. Going to retry failed tests...

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

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
169 (only retried tests)	61	0	1	0	107

⚪ 2025-03-10 11:41:45 UTC ya make is running... (failed tests rerun, try 3)
🟢 2025-03-10 12:02:44 UTC Tests successful.

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

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
152 (only retried tests)	46	0	0	0	106

🟢 2025-03-10 12:02:56 UTC Build successful.
🟢 2025-03-10 12:03:19 UTC ydbd size 2.1 GiB changed* by +61.1 KiB, which is < 100.0 KiB vs main: OK

ydbd size dash	main: a69244b	merge: e48ad20	diff	diff %
ydbd size	2 293 856 560 Bytes	2 293 919 096 Bytes	+61.1 KiB	+0.003%
ydbd stripped size	480 432 384 Bytes	480 432 448 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}