Remove Progressive Layer Dropping (PLD) support (#8562)
Removes unsupported Progressive Layer Dropping support as part of #8489.
• Remove the PLD scheduler, configuration helpers/constants, and engine
initialization, forward-pass injection, step updates, and public
accessors.
• Reject any configuration containing progressive_layer_drop with
DeepSpeedConfigError , including disabled, empty, null, and "auto"
values, instead of silently training without PLD.
• Remove PLD-specific tests, the helper model, and the HPU CI selector.
• Remove the PLD tutorial, announcement, feature listing, and navigation
entries. Retain historical publication citations.
Signed-off-by: Hongwei Chen <hongweichen@microsoft.com>
