Hybrid cache v2
Author: tugsbayasgalan
Pull request: yes

Reapply of https://github.com/huggingface/transformers/pull/37623 .

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cc @gante

@tugsbayasgalan thank you for the PR 💛  

if this PR is ready for review, then:
1. close the original PR (#37623)
2. address arthur's comment [here](https://github.com/huggingface/transformers/pull/37623#discussion_r2065980162). It's probably preferable to do it in a separate PR, and then update this one accordingly 🤗 
3. ping me again