text: Title: Rework method of updating atomic-updated data volumes
  Body: **What this PR does / why we need it**:
  
  This change affects the way that secret, configmap, downwardAPI and projected volumes (which all use the same underlying code) implement their data update functionality.
  
  * Instead of creating a subdirectory hierarchy that will contain symlinks to each actual data file, create only symlinks to items in the root of the volume, whether they be files or directories.
  * Rather than comparing the user-visible data directory to see if an update is needed, compare with the current version of the data directory.
  * Fix data dir timestamp format year
  * Create `..data` symlink even when a data volume has no data so consumers can have simplified update watch logic.
  
  **Which issue(s) this PR fixes**:
  Fixes #57421
  
  Fixes #60814 for master / 1.10
  
  **Release note**:
  ```release-note
  Fix a bug affecting nested data volumes such as secret, configmap, etc.
  ```