MID-11043 Fix 10k limit in certification queries using iterative search for native repo

[kay1313]

Description

This PR fixes an issue with certification queries on native repository where large campaigns could be silently truncated (e.g. at ~10,000 containers).

The problem was caused by using non-iterative repositoryService.searchContainers(...) in certification helpers, which may return only a limited result set for large queries on native repository. As a result, operations like stage closing or work item processing could affect only a subset of cases/work items, leaving the rest unprocessed.

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Changes

Introduced a shared native-aware helper in AccCertQueryHelper:

• uses searchContainersIterative(...) for native repository
• falls back to searchContainers(...) for non-native repository

Updated certification queries to use the helper:

• searchCases(...)
• getAllCurrentIterationCases(...)
• searchOpenWorkItems(...)

This ensures full result sets are processed for large campaigns while preserving existing behavior for non-native backends.

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Notes

• The difference between native and non-native repository behavior was introduced in MID-10225.
• This change preserves the intended behavior introduced there; it only fixes truncation of large result sets and does not alter the original logic.

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Testing

Added regression test covering large campaign (>10k cases)
Verifies:

• full case retrieval via helper methods
• correct processing of all work items during stage closing

[1azyman]

Generic repository was removed in 4.10 (via #10866). Just minor changes to remove dead code.

[1azyman]

AFAIK this is always true for midpoint 4.11 and 4.10 (generic, non-native repository module was removed in 4.10 - repo-sql-impl).

[1azyman]

10k limit in javadoc not correct, native repo supports iterative search, generic repo removed in >=4.10

[kay1313]

Removed the obsolete non-native repository fallback and the outdated Javadoc note about the 10k limit.