Fix export uploader (win build + YT)

[stanislav-shchetinin]

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[Copilot]

Pull request overview

This PR adjusts the Windows fallback implementation of SchemeShard export uploaders so that it exposes the same factory function names as the non-Windows implementation, matching the API declared in schemeshard_export_uploaders.h.

Changes:

• Renamed Windows fallback uploader factory functions to CreateSchemeUploader and CreateExportMetadataUploader (removing the Fallback suffix).

Comments suppressed due to low confidence (2)

ydb/core/tx/schemeshard/schemeshard_export_uploaders_fallback.cpp:73

• These uploader factory functions are templates defined in a .cpp file, but unlike the non-Windows implementation (schemeshard_export_uploaders.cpp) there are no explicit instantiations for the concrete settings types used by the call sites (ExportToS3Settings / ExportToFsSettings). On Windows this will typically result in unresolved symbols at link time for CreateSchemeUploader<...>. Add explicit template instantiations for the required settings types (mirroring schemeshard_export_uploaders.cpp) or move the template definitions into the header to allow implicit instantiation.

IActor* CreateSchemeUploader(TActorId schemeShard, ui64 exportId, ui32 itemIdx, TPathId sourcePathId,
    const TSettings& settings, const TString& databaseRoot, const TString& metadata,
    bool enablePermissions, bool enableChecksums, const TMaybe<NBackup::TEncryptionIV>& iv
) {
    Y_UNUSED(sourcePathId, settings, databaseRoot, metadata, enablePermissions, enableChecksums, iv);
    return new TSchemeUploaderFallback<TSettings>(schemeShard, exportId, itemIdx);

ydb/core/tx/schemeshard/schemeshard_export_uploaders_fallback.cpp:82

• Same issue as for CreateSchemeUploader: CreateExportMetadataUploader is a function template defined only in this .cpp, but this file does not explicitly instantiate it for the concrete settings types used elsewhere. This can cause unresolved symbols on Windows for CreateExportMetadataUploader<ExportToS3Settings/FsSettings>. Add explicit instantiations (or make the template definition available in the header).

NActors::IActor* CreateExportMetadataUploader(NActors::TActorId schemeShard, ui64 exportId,
    const TSettings& settings, const NKikimrSchemeOp::TExportMetadata& exportMetadata,
    bool enableChecksums
) {
    Y_UNUSED(settings, exportMetadata, enableChecksums);
    return new TExportMetadataUploaderFallback<TSettings>(schemeShard, exportId);

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[ydbot]

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[github-actions]

⚪ 2026-03-19 12:34:34 UTC Pre-commit check linux-x86_64-release-asan for 76258e8 has started.
⚪ 2026-03-19 12:35:08 UTC Artifacts will be uploaded here
⚪ 2026-03-19 12:37:06 UTC ya make is running...
🟡 2026-03-19 14:36:29 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?
17288	17262	0	17	7	2

🟢 2026-03-19 14:36:37 UTC Build successful.
🟡 2026-03-19 14:37:06 UTC ydbd size 3.9 GiB changed* by +642.4 KiB, which is >= 100.0 KiB vs main: Warning

ydbd size dash	main: 65c5043	merge: 76258e8	diff	diff %
ydbd size	4 210 095 144 Bytes	4 210 752 984 Bytes	+642.4 KiB	+0.016%
ydbd stripped size	1 572 494 304 Bytes	1 572 729 600 Bytes	+229.8 KiB	+0.015%

^{*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]

⚪ 2026-03-19 12:42:44 UTC Pre-commit check linux-x86_64-relwithdebinfo for 76258e8 has started.
⚪ 2026-03-19 12:42:48 UTC Artifacts will be uploaded here
⚪ 2026-03-19 12:44:24 UTC ya make is running...
🟡 2026-03-19 15:18:38 UTC Some tests failed, follow the links below. Going to retry failed tests...

Details

Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
46688	43155	0	2	3519	12

⚪ 2026-03-19 15:18:57 UTC ya make is running... (failed tests rerun, try 2)
🟢 2026-03-19 15:22:39 UTC Tests successful.

Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
223 (only retried tests)	218	0	0	0	5

🟢 2026-03-19 15:22:43 UTC Build successful.
🟡 2026-03-19 15:23:07 UTC ydbd size 2.4 GiB changed* by +582.7 KiB, which is >= 100.0 KiB vs main: Warning

ydbd size dash	main: de0d867	merge: 76258e8	diff	diff %
ydbd size	2 584 256 592 Bytes	2 584 853 232 Bytes	+582.7 KiB	+0.023%
ydbd stripped size	543 327 080 Bytes	543 454 664 Bytes	+124.6 KiB	+0.023%

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

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