change some event scopes from struct to namespace

[ijon]

For those components, which events are used by schemeshard and scheme operations.

When event classes are declared as inner classes of a struct, it is impossible to make forward declarations of those classes (without refactoring all those definitions in a specific way). Changing event scope from struct to namespace enables easy forwarding of event classes of that scope.

This is part of "improve schemeshard operation build-time" effort (#10633).

Changelog category

• Not for changelog

[github-actions]

⚪ 2024-10-22 11:17:00 UTC Pre-commit check linux-x86_64-release-asan for fa10c4c has started.
⚪ 2024-10-22 11:17:31 UTC Artifacts will be uploaded here
⚪ 2024-10-22 11:21:21 UTC ya make is running...
🟡 2024-10-22 13:03:28 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
11571	11353	0	61	55	102

🟢 2024-10-22 13:04:28 UTC Build successful.
🟢 2024-10-22 13:04:59 UTC ydbd size 5.7 GiB changed* by -9.0 KiB, which is <= 0 Bytes vs main: OK

ydbd size dash	main: 94d1ae0	merge: fa10c4c	diff	diff %
ydbd size	6 099 054 144 Bytes	6 099 044 880 Bytes	-9.0 KiB	-0.000%
ydbd stripped size	1 522 369 648 Bytes	1 522 367 088 Bytes	-2.5 KiB	-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]

⚪ 2024-10-22 11:17:25 UTC Pre-commit check linux-x86_64-relwithdebinfo for fa10c4c has started.
⚪ 2024-10-22 11:17:59 UTC Artifacts will be uploaded here
⚪ 2024-10-22 11:21:52 UTC ya make is running...
🟡 2024-10-22 12:41:13 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?
41403	35799	0	5	5502	97

⚪ 2024-10-22 12:44:44 UTC ya make is running... (failed tests rerun, try 2)
🟡 2024-10-22 12:56:11 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?
102 (only retried tests)	7	0	2	1	92

⚪ 2024-10-22 12:56:19 UTC ya make is running... (failed tests rerun, try 3)
🔴 2024-10-22 13:07:45 UTC Some tests failed, follow the links below.

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

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
94 (only retried tests)	1	0	1	0	92

🟢 2024-10-22 13:07:52 UTC Build successful.
🟢 2024-10-22 13:08:14 UTC ydbd size 2.8 GiB changed* by -5.4 KiB, which is <= 0 Bytes vs main: OK

ydbd size dash	main: 94d1ae0	merge: fa10c4c	diff	diff %
ydbd size	3 012 001 568 Bytes	3 011 996 080 Bytes	-5.4 KiB	-0.000%
ydbd stripped size	478 074 552 Bytes	478 074 040 Bytes	-512 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}