[docs] add Google TPU hardware guide (#49642)
* docs: add Google TPU hardware guide
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
* review(doc): change torch_tpu ->
* review(doc): drop attn_implementation in tpu
* review(doc): fix last sentences for tpu
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Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
