win: improve soft file/app delete security #260

This commit improves soft file delete logic:

- Unify logic for soft deleting single files and system apps.
- Rename `RenameSystemFile` templating function to `SoftDeleteFiles` so
  new name gives clarity to:
   - It's not necessarily single file being renamed but can be multiple
     files.
   - It's not necessarily system files being renamed, but can also work
     without granting extra permissions.
- Grant permissions for only files that will be backed up, skipping
  unnecessarily granting permissions to folders/other files. Both
  `SeRestorePrivilege` and `SeTakeownershipPrivileges` are claimed and
  revoked as necessary.
- Make granting permissions optional through `grantPermissions`
  parameter. Do not take permissions if not needed.
- Restore permissions to system default after file is renamed. Before
  both deletion of system apps and renaming system files did not restore
  their original permissions. This might leave user computers
  vulnerable, which is fixed in this commit. It ensures that the
  system's original security posture is preserved.
- Deleting system apps is now independent of `Get-AppxPackage`,
  improving its robustness and enabling their execution once system apps
  are hard-deleted (#260)
- Introduce common way to share glob iteration logic of how the
  directories are being cleaned up. It reuses most of the logic from
  former `DeleteGlob` with some improvements:
  - Simplify call to `Get-ChildItem` by avoiding `-Filter` parameter.
  - Improve reliability of getting parent directory in `DeleteGlob`
    sanity check to use .NET's `[System.IO.Path]` methods.