cache_utils: fix QuantizedLayer to correctly propagate reorder_cache, crop, and batch ops to quantized buffers

[GitGlimpse895]

What does this PR do?

QuantizedLayer maintains two separate storage regions: a full-precision
residual buffer (self.keys / self.values) and a quantized buffer
(self._quantized_keys / self._quantized_values). However, the four
mutation methods inherited from DynamicLayer — reorder_cache,
crop, batch_repeat_interleave, and batch_select_indices — only
operated on the residual buffer, silently leaving the quantized buffer
untouched.

Concrete failure modes:

• Beam search (reorder_cache): the quantized buffer stays in
  original beam order while the residual reorders, causing crossed
  attention across beams with no error raised.
• Constrained generation rollback (crop): cumulative_length
  diverges from the actual stored state, corrupting subsequent
  get_seq_length calls.
• Group beam search / contrastive decoding (batch_select_indices,
  batch_repeat_interleave): batch dimension of the quantized buffer
  is never updated, producing mismatched batch sizes between the two
  storage regions.

This PR overrides all four methods in QuantizedLayer. Since
_quantized_keys/_quantized_values are opaque backend objects for
both QuantoQuantizedLayer and HQQQuantizedLayer, the fix uses a
dequantize → operate → re-quantize pattern, which is backend-agnostic
and does not compound quantization error meaningfully beyond what is
already introduced at the original quantization step.

Fixes # (issue)

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Who can review?

@gante @SunMarc

• I confirm that this is not a pure code agent PR.