This commit resolves an issue where the ACL inheritance state (`IsInherited` property) was not being correctly restored for files and directories on Windows.

The root cause was that the `SECURITY_INFORMATION` flags used in the `SetNamedSecurityInfo` API call contained both the `PROTECTED_DACL_SECURITY_INFORMATION` and `UNPROTECTED_DACL_SECURITY_INFORMATION` flags simultaneously. When faced with this conflicting information, the Windows API defaulted to the more restrictive `PROTECTED` behavior, incorrectly disabling inheritance on restored items.

The fix modifies the `setNamedSecurityInfoHigh` function to first clear all existing inheritance-related flags from the `securityInfo` bitmask. It then adds the single, correct flag (`PROTECTED` or `UNPROTECTED`) based on the `SE_DACL_PROTECTED` control bit from the original, saved Security Descriptor.

This ensures that the API receives unambiguous instructions, allowing it to correctly preserve the inheritance state as it was at the time of backup. The accompanying test case for ACL inheritance now passes with this change.

…store

When restoring files without admin privileges, the IsInherited property
of Access Control Entries (ACEs) was not being preserved correctly.
The low-privilege restore path (setNamedSecurityInfoLow) was using a
static PROTECTED_DACL_SECURITY_INFORMATION flag, which always marked
the restored DACL as explicitly set rather than inherited.

This commit updates setNamedSecurityInfoLow to dynamically determine
the correct inheritance flag based on the SE_DACL_PROTECTED control
flag from the original security descriptor, matching the behavior of
the high-privilege path (setNamedSecurityInfoHigh).

Changes:
- Update setNamedSecurityInfoLow to accept control flags parameter
- Add logic to set either PROTECTED_DACL_SECURITY_INFORMATION or
  UNPROTECTED_DACL_SECURITY_INFORMATION based on the original SD
- Add TestRestoreSecurityDescriptorInheritanceLowPrivilege to verify
  inheritance is correctly restored in low-privilege scenarios

This ensures that both admin and non-admin restore operations correctly
preserve the inheritance state of ACLs, maintaining the original
permissions flow on child objects.

Addresses review feedback on PR for issue restic#5427

Split highSecurityFlags into highBackupSecurityFlags and
highRestoreSecurityFlags to avoid runtime bitwise operations.
This makes the code cleaner and more maintainable by using
appropriate flags for GET vs SET operations.

Addresses review feedback on PR for issue restic#5427