[core] Add helpers for common operations in mmap tests

[almilosz]

Details:

• Reduce code duplication in HintEvictTest, HintPrefetchTest and VmPrefetchMappedFileTest tests
• Added a new header and implementation (mmap_test_utils.hpp / mmap_test_utils.cpp) providing utility functions: make_prime_pattern() for generating predictable test data, and read_mapped() for extracting bytes from a mapped memory region.
• Added write_temp_file() in common_test_utils/file_utils.hpp

Tickets:

• CVS-190260

AI Assistance:

• AI assistance used: yes

[github-actions]

CI Doctor — Merge Queue failure on this PR

Pipeline: Windows (VS 2022, Python 3.11, Release)
Failure: JS API E2E Electron test cleanup fails with Permission Denied on Windows
Automatic restart: ✅ Re-run of failed jobs requested (reason: Flaky Windows Electron cleanup failure — rm permission denied on locked DLL/exe is transient and a re-run typically succeeds)

Possible remedy

1. Short-term: The failed jobs have been automatically re-run — no action needed from you.
2. Long-term fix: Update electron-app.test.js cleanup hook to use fs.rm(path, { recursive: true, force: true }) (Node 14.14+) or the rimraf npm package instead of rm -rf via exec. Windows keeps file locks on electron.exe and its DLLs, which rm cannot bypass.
3. Ensure the Electron process is fully terminated before cleanup runs (e.g., call app.quit() and wait for process exit before deleting the directory).

What happened

The JS API E2E job on a Windows runner passed its 2 actual tests, but the after all cleanup hook failed when trying to rm -rf demo-electron-app-project — Windows reported Permission denied on locked Electron dist files (electron.exe, d3dcompiler_47.dll, libEGL.dll, libGLESv2.dll). This is unrelated to this PR's changes (mmap test utilities). This exact pattern has been seen 2 times in CI history (previously on 2026-07-09, run 29010970383, PR #36780).

Generated by CI Failure Doctor — Merge Queue · 94.9 AIC · ⌖ 6.47 AIC · ⊞ 17.6K · ◷