New DynamicSlidingWindowLayer & associated Cache (#40039)
* start adding the layer
* style
* improve
* modular
* fix
* fix
* improve
* generate integration
* comment
* remove old one
* remove
* fix
* fix
* fix
* fix all recompiles
* fix
* doc
* fix
* add text config check
* fix encoderdecoder cache
* add it for all models with sliding/hybrid support
* revert
* start fixing
* prophetnet
* fsmt
* fix ddp_data
* add test for mistral
* improve mistral test and add gemma2 test
* docstrings
