GH-48788: [C++] Fix Windows mmap error code mapping in mman.h

[Manas103]

Rationale for this change

The __map_mman_error() function in cpp/src/arrow/io/mman.h was not properly mapping Windows error codes to POSIX errno values. The function contained a TODO comment and returned raw Windows error codes (DWORD values like 2, 5, 6, 112) directly instead of converting them to POSIX errno values (like ENOENT, EACCES, EBADF, ENOSPC). This broke errno-based error handling in memory mapping operations on Windows, as code expecting POSIX errno values would receive raw Windows error codes instead.

What changes are included in this PR?

• Implemented proper Windows error code to POSIX errno mapping in __map_mman_error() function
• Maps 14 common memory mapping errors (ERROR_FILE_NOT_FOUND, ERROR_ACCESS_DENIED, ERROR_NOT_ENOUGH_MEMORY, etc.) to appropriate POSIX errno values
• Mapping matches Arrow's existing WinErrorToErrno() conventions for consistency
• Maintains behavioral compatibility by using the deferr parameter (EPERM default) for unmapped errors
• Added comprehensive Windows-gated unit tests in file_test.cc covering all mapped errors, zero case, and fallback behavior

Are these changes tested?

Yes. Added TestMmanErrorMapping.MapCommonErrors test covering all mapped error codes, zero error code case, and fallback behavior. Tests are Windows-gated (#ifdef _WIN32) and will run on Windows CI.

Are there any user-facing changes?

No.

GitHub Issue: #48793

• GitHub Issue: [C++][Windows] mmap returns Win32 error codes instead of errno #48793
• GitHub Issue: GH-48788: [C++] Fix Windows mmap error code mapping in mman.h #48788

[github-actions]

Thanks for opening a pull request!

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See also:

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• Contribution Guidelines - Contributing Overview

[raulcd]

Thanks for your PR, could you open an issue and follow our PR description and naming convention guidelines?

[github-actions]

⚠️ GitHub issue #48788 has been automatically assigned in GitHub to PR creator.